Opens a new PDF document.
If different from 0, document compression is turned on
Sets the file in which the document is written. - is a synonym for stdout.
Note: Using stdout will not work if PHP is compiled as an apache module. You can solve this problem by skipping this parameter filename and using cpdf_output_buffer() later to output the PDF document.
An array defining the document limitation. See cpdf_global_set_document_limits() for more information
Returns a document handle, needed as the first parameter for all other functions of the library.