A new iPhone application called Doc Sign enables users to manage and sign PDF documents from their phones.

Doc Sign can open PDF files attached to incoming emails, from a public URL or the via Drop.io file sharing service. The user can then touch any part of the document and add text or write their signature, then save and email it back or transfer it to their desktop via iTunes.

The app does not currently support PDFs from Google Docs, but this feature is being planned for in a future version. In the meantime, users can work around this limitation by emailing files to themselves.

Doc Sign, which was released by Crowded Road last month, is not the first application to bring PDF signing to the iPhone, but it does have some features that attempt to set it apart from the competition.

"Unlike some similar products, Doc Sign is a pure app, not relying on any website or web-service," says Adam Korbl, founder and CEO of Crowded Road. "We do not store or pass user documents through our servers whatsoever. This not only avoids any reliability issues that can arise as a result of server failures, but it also ensures superior privacy and document security, something essential for any enterprise-level application."

While the application will work on older versions of the iPhone, says Korbl, Apple's new iOS4 is recommended for the best user experience.

Doc Sign is not yet available for other devices, but Crowded Road is working on versions for the iPad and Android.

Disclosure: We received a free version of this app in order to test it.