Dear Masoud,
I am delighted to hear that you would like to translate PDFreaders.org into Persian. The Free Software movement is a global one and we would love to reach out to people in Iran, Afghanistan and elsewhere. Thank you for your kind offer!
First, unless I am much mistaken, you need to register a guest account on trac.fsfe.org, which should grant you read access to our public Subversion repositories. Then you should follow the instructions at https://wiki.fsfe.org/PDFreaders#Organisation_done to check out a copy of the website. In the src directory, you should translate every file named *.en.page and name the translation *.fa.page. You may optionally provide similarly named graphics in the graphics subdirectory, but then you have to manually modify the links in the graphics.fa.page to reflect this.
The .page format is a simple markup language and you should modify only stuff that looks English. Stuff that looks technical should generally be left alone. In case of Persian there is the exception that "direction: ltr" in the header must become "direction: rtl".
Translations should be sent to translators@fsfeurope.org and it would be nice to cc contact@pdfreaders.org. Make it clear in the subject line that the message contains a Persian translation of a page on pdfreaders.org. This way hopefully someone can proofread them before I commit them to pdfreaders.org.
If you do not know how to use Subversion, I can checkout the latest revision for you and upload it somewhere. If you have any other questions, do not hesitate to contact me.
P.S. You are probably aware of this, but make sure that any translations also reflect this: We talk about Free Software, not Open Source or (even worse!) gratis software, bud we do talk about Open Standards. It is crucial that any translations reflect this aspect of our rhetoric accurately.
Thank you for your kind offer!
Sincerely yours,