I've been researching a lot about link building via distributing .pdf files and it looks promising. Has anyone had any experience with this?
Yes, it works but make sure your link is used in relevant niches. I wrote an "how to" article, in the DIY sector and used open office to create the PDF (free download), now I put my keyword in the header of the letter and now when I search keywords the PDFs are picked up as they are re-published on DIY sites.