Docstoc, a service for embedding documents in web pages, has raised $3.25 million in fresh capital from Rustic Canyon Partners, following an angel round of $750,000 that we reported on late last year.

While Docstoc and rival Scribd tout their respective services as ways to share documents and engage your community – especially with us social media types – I see the value much more as their ability to eventually kill the notion of attaching files to emails, or linking people to downloads. Email attachments are annoying – they slow down your computer, often don’t work (especially between Office ’08 users and non-users), and, if you don’t have proper virus protection, can be instant system death.

Embeddable docs, on the other hand, allow you to embed everything from PowerPoints to PDF files onto a web page (example below), which eliminate all of the above problems and pet peeves. For me, and a lot of folks who frequently deal with attachments, I think this is the big value proposition of Docstoc and Scribd, however, it’s not presently the primary way they pitch the service or plan to make money.

One way Docstoc does plan to make money is with a new Content Partnership Program that they announced along with their funding news. This program allows content uploaders to include advertising, or sell premium content (Scribd offers something similar with their recent iPaper launch). For Docstoc, this makes a lot of sense, since they focus on “professional” documents – saving people time on finding templates for contracts and other types of business docs is something that has already been proven by others as a viable business model. In a sense, this is a replacement for online white papers, research reports, and eBooks, which are typically marketed and sold as PDFs – a step in the right direction for eliminating unnecessary downloads, but not “the death of attachments” that I dream about.

However, my dreams may soon come true as Docstoc moves towards opening up an API for developers. For example, imagine an application or plugin that automatically converted email attachments into embedded docs instead. That’s the type of service people would pay for, and one that could make both the developer and Docstoc a lot of money. An API and partnerships with the types of software companies that could make such convenience possible are both on tap for DocStoc this year, according to CEO Jason Nazar.

While there is plenty of value in what Docstoc and Scribd currently do – which is connect people to information previously trapped in downloads – the value of what they could do in the future is enormous – and something that potentially could be used by every Web user. Which of these two companies is best positioned to execute on this vision? While presently the underdog (at least in terms of traffic), with its focus on professional documents and users, Docstoc might have the edge.

Meanwhile, here’s Docstoc’s presentation outlining their new Content Partnership Program, in convenient embedded format: