Not sure if I understand correctly.. You want to buy a pdf? Actually, download is free for everyone (in consideration of the local copyright...), so why you want to buy it?! Well, you can donate if you want, then click the corresponding link the menu. Download is with 15sec waiting period for everyone/non-members, and if you want to get rid of it you can become member (including access to Naxos music library).
Or did you mean music which is not public domain in your country where you live? Then no, IMSLP doesn't "sell" pdfs, not to my knowledge. If you want to buy a printed edition, you must go to sites like sheetmusic plus, amazon, and many others who sell scores.
HP
