The main program for viewing PDF files is Adobe Acrobat Reader or Adobe Reader The program has evolved into a huge version of its development allowing space for the work of other companies that were able to provide smaller and lighter programs to open PDF files but in any case the best program and the ultimate solution to open PDF files In case of problems with other programs it is Adobe Acrobat Reader which cannot be ignored anyway and hence Downloader puts it as the main program however as the main developer of Adobe PDF technology the first versions that can support all the new features of PDF files are Adobe readers.