DocStoc, a popular site for uploading and sharing business documents, is opening the doors to its DocStore document marketplace today. Since the DocStore launch in August, the Los Angeles company has been working with a few select partners, but now anyone can apply to sell in the marketplace.

DocStoc is often compared to document-sharing site Scribd, which also has a marketplace, but the stated aims of the two stores are pretty different — the Scribd store is an e-book marketplace that’s suppsoed to be an Amazon alternative, while the DocStore is a way to way to sell documents useful for small businesses, for example legal forms or contract templates.

In order to sell in the DocStore, companies must apply at the website. But once you’re approved, you can upload documents and set the pricing as you wish. The revenue is split 50-50 with DocStoc, but the company is launching the seller program with a promotion where you can keep all of your sales revenue for the first 60 days. Other features include analytics to see who is viewing your document, the ability to sell a bundle of documents at special pricing, and an embed feature for showing previews of documents for sale on your website.

Chief executive Jason Nazar said he expects the vast majority (like, 95 percent) of DocStoc’s content to remain free, but the DocStore should account for the majority of the company’s revenue going forward (it also runs advertising with some documents).

I also asked Nazar how he sees the document-sharing marketplace evolving. On a basic level, sites like Scribd and DocStoc have a similar product, he acknowledged, but over time they’re starting to differentiate.

“I think there’s going to be a small set of players that successfully build up marketshare as far as users, and then they’re going to differentiate in terms of the users they reach, and how they serve them,” Nazar said.

DocStoc has raised $4 million in funding and says it has 20 million monthly unique visitors.