PDF is Portable Document Format that was created by Adobe Systems in 1993 for desktop publishing use. Readers for many platforms are available, such as Adobe Acrobat Reader, Foxit, Preview, Xpdf, Evince, Okular, and KPDF. Most PDF readers are generally use for free.

PdfArticles.com provide the largest free resources of PDF files. All files based on popular topics and most search by people.