Acrobat Reader is the most popular and powerful tool for viewing PDF files. There are free alternatives to Adobe Acrobat.
PrimoPDF.com – PrimoPDF Create PDF files from any printable document (300+ file types).
Foxit Reader for Windows – Foxit Reader is a free PDF document viewer. Foxit Reader 2.3 is just released. The new version 2.3 includes a multimedia player feature allowing Foxit users to not only read PDFs, but to watch and listen to the audio/video elements coming with PDFs as well.
Foxit Reader supports Windows Me/2000/XP/2003/Vista.
PDFTextOnline – PDFTextOnline allows you to access the text and metadata held in your PDF documents. It handles all fonts and languages (including Chinese, Japanese, Korean, and more).
PDF-XChange Viewer – PDF-XChange Viewer is an alternative viewer for PDF files that enables you to view and annotate PDF files.
Sumatra PDF – Sumatra PDF is a slim, free, open-source PDF viewer for Windows. It requires Windows 2000 or newer (XP, Vista). Windows 95, 98 and ME are not supported.