What is FPDF?

FPDF is a PHP class which allows to generate PDF files with pure PHP, that is to say without using the PDFlib library. The advantage is that PDFlib requires a fee for a commercial usage. F from FPDF stands for Free: you may use it for any kind of usage and modify it to suit your needs.

FPDF has other advantages: high level functions. Here is a list of its main features:

Choice of measure unit, page format and margins
Page header and footer management
Automatic page break
Automatic line break and text justification
Image support (JPEG and PNG)
Colors
Links
TrueType, Type1 and encoding support
Page compression
FPDF requires no extension (except Zlib to activate compression) and works with PHP4 and PHP5.

http://www.fpdf.org/

UFPDF works the same as FPDF, except that all text is in UTF-8, so consult the FPDF documentation for usage.

FPDI is a collection of PHP classes that allow developers to read pages from existing PDF documents and to use them as templates in FPDF by Olivier Plathey. The whole idea is based upon an article in the magazine php|architect by Marco Tabini. Apart from a copy of FPDF, FPDI does not require any special PHP extensions.

FPDI Import existing PDF documents into FPDF