http://i.cnn.net/cnn/interactive/allpolitics/0706/popup.congress.earmarks/pdfs/tx.14.paul.pdf
HOWEVER, if that does point to his campaign sight, that is a highly illegal violation of campaign laws. I’ll have to zoom in and look carefully, but I doubt even Paul would be that careless.
The phone number in the letter is what concerns me. It points to his PAC site.
I’m wondering if the small writing at the bottom says something along the lines of “Not for official use” or “Paid for by friends of Ron Paul” If it says that, then the letter is legal. If the letter originated from his official office and is on taxpayer funded stationery, though, then he is in violation.
The stationery in the link has a different heading than your picture. Therefore it’s quite likely that he’s safe and has used “campaign stationery” for the letter containing the phone number of his PAC.