Some PDFs are simply write-protected by the author, preventing anyone else from editing them. It's also possible to prevent files from being saved, copied, etc. The only solution is to contact the author and request a copy that is not write-protected.
As to CDs, keep in mind that neither CD-Rs nor CD-RWs let you modify documents at will. The only way you can do that on CD-RWs is using packet-writing software such as DLA (Drive Letter Access), which must be installed on each computer you plan on modifying the contents on. Otherwise you must copy the entire CD's contents to the hard drive, edit the file(s), wipe the CD, then burn all of the data back to the disc.
John
P.S. Please see the forum sticky concerning future technical questions.
i need to be able to download various forms from sites to work on them
and to work on files emailed to me. i need to have these as RW. i've read various answers in these forums,none are satisfactory.copying to the harddisk and editing there does not work,and is sometimes prevented by the windows software. does anyone know of a reliable programme that will allow download of Adobe PDF/ Word documents as RW and their subsequent copying to CD-RWs. Thanks.

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