Google continued to augment its Gmail application Friday by adding the ability to view Adobe PDF files in the Web mail application.

Now you'll see a new View link next to PDF attachments you receive in Gmail. Click this link and the PDF opens inside the browser.

Sound familiar? It should if you're a Google Docs user. Google already added this PDF View link to Google Docs last June.

As Webware's Josh Lowensohn notes, the option to open up PDFs as HTML pages straight from the message is gone, but users can still view in plain HTML from a link at the top of the new viewer, and download PDFs while offline through the Download link net to the View Link.

PDF reading, unlike the voice and video chat Google launched in Gmail last month, is itself not a huge deal. But it points to a more significant trend that bears watching: The evolution of Gmail as your one-stop UCC (unified communications and collaboration) hub.

Google recognizes that it is important to embrace popular file format technologies, even from rivals such as Adobe and Microsoft, to please Gmail users looking to share information.

Moreover, as an upstart in UCC, it is also incumbent on Google to continue to add features that will keep users within Gmail and the other Google Apps, such as Docs. PDF viewing is such a utility.

From small features such as PDF viewing and task manager, to more significant tools like voice and video chat and SMS chat, 2008 may well be remembered as the year Google seriously began its stealth attack on the UCC technology stockpiles of Microsoft, IBM and Cisco -- with Gmail no less.

Who would have thought that would be the case when Google began innocently inviting certain people to Gmail 5 years ago? It's clear that just as e-mail is the hub for social networking, it's become the hub for UCC, at least for Web services providers like Google.

It will be interesting to see how Google continues along this path in 2009, and even more fun to chronicle.