4. File format

Figure 2 describes the structure of a PDF file, made up of four sections: the header, the body, the cross-reference table and the final section.

The header consists of a single line that identifies the file as being in PDF format and indicates the PDF version. For example, %PDF-1.1. The body of the file contains a list of PDF objects, expressed with a syntax almost identical to that of PostScript. The table of indirect references provides quick access to a PDF object in the file. The final section enables a program to quickly find the table of indirect references.

To sum up, PDF syntax is made up of integers or floats, names, strings and operators used to create more complex objects: tables, association tables or dictionaries. Names are essentially used as keys...