1 Basic Usage

The Coherent PDF tools provide a wide range of facilities for modifying PDF files created by other means. There is a single command-line program cpdf (cpdf.exe under Microsoft Windows). The rest of this manual describes the options that may be given to this program.

1.1 Documentation

The operation -help / --help prints each operation and option together with a short description. The operation -version prints the cpdf version string.

1.2 Input and Output Files

Files on the command line are distinguished from other input by their containing a period. If an input file does not contain a period, it should be preceded by -i. For example:

To restrict cpdf to files ending in .pdf (in upper or lower or mixed case) add the option -idir-only-pdfs before -idir:

1.3 Input Ranges

An input range may be specified after each input file. This is treated differently by each operation. For instance

1.4 Working with Encrypted Documents

In order to perform many operations, encrypted input PDF files must be decrypted. Some require the owner password, some either the user or owner passwords. Either password is supplied by writing user=<password> or owner=<password> following each input file requiring it (before or after any range). The document will not be re-encrypted upon writing. For example:

To re-encrypt the file with its existing encryption upon writing, which is required if only the user password was supplied, but allowed in any case, add the -recrypt option:

The password required (owner or user) depends upon the operation being performed. Separate facilities are provided to decrypt and encrypt files (See Section 4).

When appropriate passwords are not available, the option -decrypt-force may be added to the command line to process the file regardless.

1.5 Standard Input and Standard Output

Thus far, we have assumed that the input PDF will be read from a file on disk, and the output written similarly. Often it’s useful to be able to read input from stdin (Standard Input) or write output to stdout (Standard Output) instead. The typical use is to join several programs together into a pipe, passing data from one to the next without the use of intermediate files. Use -stdin to read from standard input, and -stdout to write to standard input, either to pipe data between multiple programs, or multiple invocations of the same program. For example, this sequence of commands (all typed on one line)

extracts the last five pages of in.pdf in the correct order, writing them to out.pdf. It does this by reversing the input, taking the first five pages and then reversing the result.

To supply passwords for a file from -stdin, use -stdin-owner <password> and/or -stdin-user <password>.

Using -stdout on the final command in the pipeline to output the PDF to screen is not recommended, since PDF files often contain compressed sections which are not screen-readable.

Several cpdf operations write to standard output by default (for example, listing fonts). A useful feature of the command line (not specific to cpdf) is the ability to redirect this output to a file. This is achieved with the > operator:

1.6 Doing Several Things at Once with AND

The keyword AND can be used to string together several commands in one. The advantage compared with using pipes is that the file need not be repeatedly parsed and written out, saving time.

To use AND, simply leave off the output specifier (e.g -o) of one command, and the input specifier (e.g filename) of the next. For instance:

1.7 Units

When measurements are given to cpdf, they are in points (1 point = 1/72 inch). They may optionally be followed by some letters to change the measurement. The following are supported:

For example, one may write 14mm or 21.6in. In addition, the following letters stand, in some operations (-scale-page, -scale-to-fit, -scale-contents, -shift, -mediabox,
-crop) for various page dimensions:

For example, we may write PMINXPMINY to stand for the coordinate of the lower left corner of the page.

Simple arithmetic may be performed using the words add, sub, mul and div to stand for addition, subtraction, multiplication and division. For example, one may write 14in sub 30pt or PMINX mul 2

1.8 Setting the Producer and Creator

The -producer and -creator options may be added to any cpdf command line to set the producer and/or creator of the PDF file. If the file was converted from another format, the creator is the program producing the original, the producer the program converting it to PDF.

1.9 PDF Version Numbers

When an operation which uses a part of the PDF standard which was introduced in a later version than that of the input file, the PDF version in the output file is set to the later version (most PDF viewers will try to load any PDF file, even if it is marked with a later version number). However, this automatic version changing may be suppressed with the -keep-version option. If you wish to manually alter the PDF version of a file, use the -set-version operation described in Section 18.5.

1.10 File IDs

PDF files contain an ID (consisting of two parts), used by some workflow systems to uniquely identify a file. To change the ID, behavior, use the -change-id operation. This will create a new ID for the output file.

1.11 Linearization

Linearized PDF is a version of the PDF format in which the data is held in a special manner to allow content to be fetched only when needed. This means viewing a multipage PDF over a slow connection is more responsive. By default, cpdf does not linearize output files. To make it do so, add the -l option to the command line, in addition to any other command being used. For example:

This requires the existence of the external program cpdflin which is provided with commercial versions of cpdf. This must be installed as described in the installation documentation provided with your copy of cpdf. If you are unable to install cpdflin, you must use -cpdflin to let cpdf know where to find it:

In extremis, you may place cpdflin and its resources in the current working directory, though this is not recommended. For further help, refer to the installation instructions for your copy of cpdf.

To keep the existing linearization status of a file (produce linearized output if the input is linearized and the reverse), use -keep-l instead of -l.

1.12 Object Streams

PDF 1.5 introduced a new mechanism for storing objects to save space: object streams. by default, cpdf will preserve object streams in input files, creating no more. To prevent the retention of existing object streams, use -no-preserve-objstm:

To create new object streams if none exist, or augment the existing ones, use -create-objstm:

Files written with object streams will be set to PDF 1.5 or higher, unless -keep-version is used (see above).

1.13 Malformed Files

There are many malformed PDF files in existence, including many produced by otherwise-reputable applications. cpdf attempts to correct these problems silently.

Grossly malformed files will be reconstructed. The reconstruction progress is shown on stderr (Standard Error):

If cpdf cannot reconstruct a malformed file, it is able to use the gs program to try to reconstruct the PDF file, if you have it installed. For example, if gs is installed and in your path, we might try:

If the malformity lies inside an individual page of the PDF, rather than in its gross structure, cpdf may appear to succeed in reconstruction, only to fail when processing a page (e.g when adding text). To force the use of gs to pre-process such files so cpdf cannot fail on them, use -gs-malformed-force:

The command line for -gs-malformed-force must be of precisely this form. Sometimes, on the other hand, we might wish cpdf to fail immediately on any malformed file, rather than try its own reconstruction process. The option -error-on-malformed achieves this.

Sometimes (old, pre-ISO standardisation) files can be technically well-formed but use inefficient PDF constructs. If you are sure the input files you are using are well formed, the -fast option may be added to the command line (or, if using AND, to each section of the command line). This will use certain shortcuts which speed up processing, but would fail on badly-produced files. The -fast option may be used with:

1.14 Error Handling

When cpdf encounters an error, it exits with code 2. An error message is displayed on stderr (Standard Error). In normal usage, this means it’s displayed on the screen. When a bad or inappropriate password is given, the exit code is 1.

1.15 Control Files

Some operating systems have a limit on the length of a command line. To circumvent this, or simply for reasons of flexibility, a control file may be specified from which arguments are drawn. This file does not support the full syntax of the command line. Commands are separated by whitespace, quotation marks may be used if an argument contains a space, and the sequence ' " may be used to introduce a genuine quotation mark in such an argument.

Several -control arguments may be specified, and may be mixed in with conventional command-line arguments. The commands in each control file are considered in the order in which they are given, after all conventional arguments have been processed. It is recommended to use -args in all new applications. However, -control will be supported for legacy applications.

To avoid interference between -control and AND, a new mechanism has been added. Using -args in place of -control will perform direct textual substitution of the file into the command line, prior to any other processing.

1.16 String Arguments

Command lines are handled differently on each operating system. Some characters are reserved with special meanings, even when they occur inside quoted string arguments. To avoid this problem, cpdf performs processing on string arguments as they are read.

A backslash is used to indicate that a character which would otherwise be treated specially by the command line interpreter is to be treated literally. For example, Unix-like systems attribute a special meaning to the exclamation mark, so the command line

1.17 Text Encodings

Some cpdf commands write text to standard output, or read text from the command line or configuration files. These are:

Add -utf8 to use Unicode UTF8, -stripped to convert to 7 bit ASCII by dropping any high characters, or -raw to perform no processing. The default unless specified in the documentation for an individual operation is -stripped.

1.18 Font Embedding

Use the -no-embed-font to avoid embedding the Standard 14 Font metrics when adding text with -add-text.

C Interface

/* CHAPTER 0. Preliminaries */

/* The function cpdf_startup(argv) must be called before using the library. */
void cpdf_startup(char **);

/* Return the version of the cpdflib library as a string */
char *cpdf_version();

/*
* Some operations have a fast mode. The default is slow mode, which works
* even on old-fashioned files. For more details, see section 1.13 of the
* CPDF manual. These functions set the mode globally.
*/
void cpdf_setFast();
void cpdf_setSlow();

/*
* Errors. cpdf_lastError and cpdf_lastErrorString hold information about the
* last error to have occurred. They should be consulted after each call. If
* cpdf_lastError is non-zero, there was an error, and cpdf_lastErrorString
* gives details. If cpdf_lastError is zero, there was no error on the most
* recent cpdf call.
*/
extern int cpdf_lastError;
extern char *cpdf_lastErrorString;

/* cpdf_clearError clears the current error state. */
void cpdf_clearError(void);

/*
* cpdf_onExit is a debug function which prints some information about
* resource usage. This can be used to detect if PDFs or ranges are being
* deallocated properly. Contrary to its name, it may be run at any time.
*/
void cpdf_onExit(void);

/* CHAPTER 1. Basics */

/*
* cpdf_fromFile(filename, userpw) loads a PDF file from a given file. Supply
* a user password (possibly blank) in case the file is encrypted. It wont be
* decrypted, but sometimes the password is needed just to load the file.
*/
int cpdf_fromFile(const char[], const char[]);

/*
* cpdf_fromFileLazy(pdf, userpw) loads a PDF from a file, doing only minimal
* parsing. The objects will be read and parsed when they are actually
* needed. Use this when the whole file wont be required. Also supply a user
* password (possibly blank) in case the file is encrypted. It wont be
* decrypted, but sometimes the password is needed just to load the file.
*/
int cpdf_fromFileLazy(const char[], const char[]);

/*
* cpdf_fromMemory(data, length, userpw) loads a file from memory, given a
* pointer and a length, and the user password.
*/
int cpdf_fromMemory(void *, int, const char[]);

/*
* cpdf_fromMemory(data, length, userpw) loads a file from memory, given a
* pointer and a length, and the user password, but lazily like
* cpdf_fromFileLazy.
*/
int cpdf_fromMemoryLazy(void *, int, const char[]);

/* Standard page sizes. */
enum cpdf_papersize {
  cpdf_a0portrait,        /* A0 portrait */
  cpdf_a1portrait,        /* A1 portrait */
  cpdf_a2portrait,        /* A2 portrait */
  cpdf_a3portrait,        /* A3 portrait */
  cpdf_a4portrait,        /* A4 portrait */
  cpdf_a5portrait,        /* A5 portrait */
  cpdf_a0landscape,       /* A0 landscape */
  cpdf_a1landscape,       /* A1 landscape */
  cpdf_a2landscape,       /* A2 landscape */
  cpdf_a3landscape,       /* A3 landscape */
  cpdf_a4landscape,       /* A4 landscape */
  cpdf_a5landscape,       /* A5 landscape */
  cpdf_usletterportrait,  /* US Letter portrait */
  cpdf_usletterlandscape, /* US Letter landscape */
  cpdf_uslegalportrait,   /* US Legal portrait */
  cpdf_uslegallandscape   /* US Legal landscape */
};

/* Remove a PDF from memory, given its number. */
void cpdf_deletePdf(int);

/*
* Calling cpdf_replacePdf(a, b) places PDF b under number a. Number b is no
* longer available.
*/
void cpdf_replacePdf(int, int);

/*
* To enumerate the list of currently allocated PDFs, call
* cpdf_startEnumeratePDFs which gives the number, n, of PDFs allocated, then
* cpdf_enumeratePDFsInfo and cpdf_enumeratePDFsKey with index numbers from
* 0...(n - 1). Call cpdf_endEnumeratePDFs to clean up.
*/
int cpdf_startEnumeratePDFs(void);
int cpdf_enumeratePDFsKey(int);
char *cpdf_enumeratePDFsInfo(int);
void cpdf_endEnumeratePDFs(void);

/* Convert a figure in centimetres to points (72 points to 1 inch) */
double cpdf_ptOfCm(double);

/* Convert a figure in millimetres to points (72 points to 1 inch) */
double cpdf_ptOfMm(double);

/* Convert a figure in inches to points (72 points to 1 inch) */
double cpdf_ptOfIn(double);

/* Convert a figure in points to centimetres (72 points to 1 inch) */
double cpdf_cmOfPt(double);

/* Convert a figure in points to millimetres (72 points to 1 inch) */
double cpdf_mmOfPt(double);

/* Convert a figure in points to inches (72 points to 1 inch) */
double cpdf_inOfPt(double);

/*
* A page range is a list of page numbers used to restrict operations to
* certain pages. A page specification is a textual description of a page
* range, such as "1-12,18-end". Here is the syntax:
*
* o A range must contain no spaces.
*
* o A dash (-) defines ranges, e.g. 1-5 or 6-3.
*
* o A comma (,) allows one to specify several ranges, e.g. 1-2,4-5.
*
* o The word end represents the last page number.
*
* o The words odd and even can be used in place of or at the end of a page
* range to restrict to just the odd or even pages.
*
* o The words portrait and landscape can be used in place of or at the end of
* a page range to restrict to just those pages which are portrait or
* landscape. Note that the meaning of "portrait" and "landscape" does not
* take account of any viewing rotation in place (use cpdf_upright first, if
* required). A page with equal width and height is considered neither
* portrait nor landscape.
*
* o The word reverse is the same as end-1.
*
* o The word all is the same as 1-end.
*
* o A tilde (˜) defines a page number counting from the end of the document
* rather than the beginning. Page ˜1 is the last page, ˜2 the penultimate
* page etc.
*/

/*
* cpdf_parsePagespec(pdf, range) parses a page specification with reference
* to a given PDF (the PDF is supplied so that page ranges which reference
* pages which do not exist are rejected).
*/
int cpdf_parsePagespec(int, const char[]);

/*
* cpdf_validatePagespec(range) validates a page specification so far as is
* possible in the absence of the actual document. Result is true if valid.
*/
int cpdf_validatePagespec(const char[]);

/*
* cpdf_stringOfPagespec(pdf, range) builds a page specification from a page
* range. For example, the range containing 1,2,3,6,7,8 in a document of 8
* pages might yield "1-3,6-end"
*/
char *cpdf_stringOfPagespec(int, int);

/* cpdf_blankRange() creates a range with no pages in. */
int cpdf_blankRange(void);

/* cpdf_deleteRange(range) deletes a range. */
void cpdf_deleteRange(int);

/*
* cpdf_range(from, to) builds a range from one page to another inclusive. For
* example, cpdf_range(3,7) gives the range 3,4,5,6,7
*/
int cpdf_range(int, int);

/* cpdf_all(pdf) is the range containing all the pages in a given document. */
int cpdf_all(int);

/*
* cpdf_even(range) makes a range which contains just the even pages of
* another range.
*/
int cpdf_even(int);

/*
* cpdf_odd(range) makes a range which contains just the odd pages of another
* range.
*/
int cpdf_odd(int);

/*
* cpdf_rangeUnion(a, b) makes the union of two ranges giving a range
* containing the pages in range a and range b.
*/
int cpdf_rangeUnion(int, int);

/*
* cpdf_difference(a, b) makes the difference of two ranges, giving a range
* containing all the pages in a except for those which are also in b.
*/
int cpdf_difference(int, int);

/* cpdf_removeDuplicates(range) deduplicates a range, making a new one. */
int cpdf_removeDuplicates(int);

/* cpdf_rangeLength gives the number of pages in a range. */
int cpdf_rangeLength(int);

/*
* cpdf_rangeGet(range, n) gets the page number at position n in a range,
* where n runs from 0 to rangeLength - 1.
*/
int cpdf_rangeGet(int, int);

/*
* cpdf_rangeAdd(range, page) adds the page to a range, if it is not already
* there.
*/
int cpdf_rangeAdd(int, int);

/*
* cpdf_isInRange(range, page) returns true if the page is in the range,
* false otherwise.
*/
int cpdf_isInRange(int, int);

/* cpdf_pages(pdf) returns the number of pages in a PDF. */
int cpdf_pages(int);

/*
* cpdf_pagesFast(password, filename) returns the number of pages in a given
* PDF, with given user encryption password. It tries to do this as fast as
* possible, without loading the whole file.
*/
int cpdf_pagesFast(const char[], const char[]);

/*
* cpdf_toFile (pdf, filename, linearize, make_id) writes the file to a given
* filename. If linearize is true, it will be linearized if a linearizer is
* available. If make_id is true, it will be given a new ID.
*/
void cpdf_toFile(int, const char[], int, int);

/*
* cpdf_toFileExt (pdf, filename, linearize, make_id, preserve_objstm,
* generate_objstm, compress_objstm) writes the file to a given filename. If
* make_id is true, it will be given a new ID.  If preserve_objstm is true,
* existing object streams will be preserved. If generate_objstm is true,
* object streams will be generated even if not originally present. If
* compress_objstm is true, object streams will be compressed (what we
* usually want). WARNING: the pdf argument will be invalid after this call,
* and should be discarded.
*/
void cpdf_toFileExt(int, const char[], int, int, int, int, int);

/*
* cpdf_toFileMemory (pdf, linearize, make_id, &length) writes a PDF file it
* and returns the buffer. The buffer length is filled in &length.
*/
void *cpdf_toMemory(int, int, int, int *);

/*
* cpdf_isEncrypted(pdf) returns true if a documented is encrypted, false
* otherwise.
*/
int cpdf_isEncrypted(int);

/*
* cpdf_decryptPdf(pdf, userpw) attempts to decrypt a PDF using the given
* user password. The error code is non-zero if the decryption fails.
*/
void cpdf_decryptPdf(int, const char[]);

/*
* cpdf_decryptPdfOwner(pdf, ownerpw) attempts to decrypt a PDF using the
* given owner password. The error code is non-zero if the decryption fails.
*/
void cpdf_decryptPdfOwner(int, const char[]);

/*
* File permissions. These are inverted, in the sense that the presence of
* one of them indicates a restriction.
*/
enum cpdf_permission {
  cpdf_noEdit,     /* Cannot edit the document */
  cpdf_noPrint,    /* Cannot print the document */
  cpdf_noCopy,     /* Cannot copy the document */
  cpdf_noAnnot,    /* Cannot annotate the document */
  cpdf_noForms,    /* Cannot edit forms in the document */
  cpdf_noExtract,  /* Cannot extract information */
  cpdf_noAssemble, /* Cannot assemble into a bigger document */
  cpdf_noHqPrint   /* Cannot print high quality */
};

/*
* Encryption methods. Suffixes false and true indicates lack of or
* presence of encryption for XMP metadata streams.
*/
enum cpdf_encryptionMethod {
  cpdf_pdf40bit,          /* 40 bit RC4 encryption */
  cpdf_pdf128bit,         /* 128 bit RC4 encryption */
  cpdf_aes128bitfalse,    /* 128 bit AES encryption, do not encrypt
                           * metadata. */
  cpdf_aes128bittrue,     /* 128 bit AES encryption, encrypt metadata */
  cpdf_aes256bitfalse,    /* Deprecated. Do not use for new files */
  cpdf_aes256bittrue,     /* Deprecated. Do not use for new files */
  cpdf_aes256bitisofalse, /* 256 bit AES encryption, do not encrypt
                           * metadata. */
  cpdf_aes256bitisotrue   /* 256 bit AES encryption, encrypt metadata */
};

/*
* cpdf_toFileEncrypted(pdf, encryption_method, permissions,
* permission_length, owner_password, user password, linearize, makeid,
* filename) writes a file as encrypted.
*/
void cpdf_toFileEncrypted(int, int, int *, int, const char[], const char[], int,
                          int, const char[]);

/*
* cpdf_toFileEncryptedExt(pdf, encryption_method, permissions,
* permission_length, owner_password, user_password, linearize, makeid,
* preserve_objstm, generate_objstm, compress_objstm, filename) WARNING: the
* pdf argument will be invalid after this call, and should be discarded.
*/
void cpdf_toFileEncryptedExt(int, int, int *, int, const char[], const char[],
                             int, int, int, int, int, const char[]);

/*
* cpdf_hasPermission(pdf, permission) returns true if the given permission
* (restriction) is present.
*/
int cpdf_hasPermission(int, enum cpdf_permission);

/*
* cpdf_encryptionKind(pdf) return the encryption method currently in use on
* a document.
*/
enum cpdf_encryptionMethod cpdf_encryptionKind(int);

Chapter 1Basic Usage