PDF

PDF (Portable Document Format) is a file format with the same file extension to identify it. PDFs are used for online copies of print documentation.

It should be noted that PDFs should only be used for documents that are intended to be printed out before being read. Many documents are published on the web in pdf form instead of html. HTML is usually better, since users don't have to load a separate pdf reader in addition to their web browser. HTML also can be searched much easier then PDFs, and html can be scrolled through easier. In case of doubt, use html.

Programs that support PDF

 * OpenOffice.org and Libre Office - can output to PDF files
 * kprinter - can make your files in any application be printed to PDF
 * ghostscript
 * ghostview
 * xpdf
 * imagemagick - lets you treat them as a picture
 * acroread - Adobe Acrobat Reader for Linux. Allows conversion to PostScript
 * evince - GNOME document viewer for multiple document formats

Programs that can manipulate PDF files
To combine, merge or otherwise manipulate PDF files, there are several alternatives:
 * PDF-Shuffler - GUI which can merge or split PDF files (also rotate, crop and rearrange pages)
 * xournal - lets you annotate directly on PDF files
 * pdfsam - java utility to split and merge PDF files
 * Final Page - gnome based GUI to reorganize, split and merge PDF documents
 * Ghostscript (see external links)
 * joinPDF (see external links)
 * pdfmeld (see external links)
 * PDF Editor
 * PDFtk Here is an Linux.com article describing PDF Toolkit (pdftk) in more detail
 * pdfjam
 * konq-pdf - a KDE service menu for PDF documents
 * krop - simple graphical tool to crop the pages of PDF files; especially useful to split pages into subpages to fit the limited screensize of devices such as eReaders.
 * briss - simple cross-platform (Linux, Windows, Mac OSX) application for cropping PDF files. A simple user interface lets you define exactly the crop-region by fitting a rectangle on the visually overlaid pages.