The majority of forms on Blanker.org is presented in the standard formats for bussiness documents. On that case if you do not know what program to use for review and printing of forms, the following is the appropriate program and it's free analogue.
RTF — the format is supported by the majority of text editors. The most widespread Microsoft Word, its free analogue OpenOffice Writer.
DOC — the file in Microsoft Word format, since recent time package OpenOffice as supports this format. Microsoft releases a specialised free resource for review of this format/
XLS — the file in Microsoft Excel format, OpenOffice package can as it to view.
PDF — format Portable Data File, a file can be viewed by Adobe Acrobat Reader.