Google Webmaster Tools has the ability to explore the internal links and external links or backlinks information for a given domain, instead of relying on the infrequently updated and wildly inaccurate link: operator within a Google search. Traditionally the link information within Google Webmaster Tools has displayed links, that were sourced or crawled from, what would otherwise be considered standard web formats such as HTML.
For a long time, Google has been indexing numerous non-web specific file formats such as Microsoft Word, Microsoft Excel, Adobe PDF and Macromedia now Adobe Flash file formats. While they were indexing and ranking those documents to show up in search, I have never seen anything to suggest that Google was counting either links or plain text URLs within those documents as a ranking indicator specifically. However, while viewing backlink data for a domain recently I noticed that Google Webmaster Tools was reporting backlinks from Adobe PDF and Microsoft Word documents.
If you’re in the business of generating a lot of documents to provide to third parties, a certain number of your clients will put the document on their web site for their users. If that happens, you’ve just gained additional inbound links to your site using the link text of your choice. If it turns out that Google is counting PDF, Word and other file format links as a ranking indicator – a savvy marketer might even recommend to third parties that they upload the document to their site – for any number of reasons, least of which is search engine optimisation.