If you are using a business process management or workflow application like Procx, you can maximize the benefit and your ROI if you use a document management system.
A document management system provides a central repository for documents (any kind of documents), versioning, metadata for documents, advance search capabilities and other collaboration tools (like discussion forums, contact lists, task management, schedules, etc.) that will let you collaborate with the whole company in a better way.
Out of the box, SkyXoft Procx supports Microsoft SharePoint Portal Server 2003 and Windows SharePoint Services (the free version) as a document management system (also supports physical folders). But not only provides support, it also adds integration and a series of tasks that can be used at any moment during your process.
When you define a process in Procx, you can attach it to a document library in SharePoint. Any document created or saved in the the library will automatically start the process. You can also assign processes to folders inside document libraries, and not having to create multiple document libraries for various processes.
Some of the tasks you can use in your process include the Lock Document and Unl
ock Document that allows you to check-in and check-out a document from a document library and preventing other people from modifying it during the process execution. You also have the Copy Document and Move Document that allows, as the name implies, to copy or move a document. But, not only do this, it can copy or move the document across document libraries or across document libraries of different sites and also (as is this was not enough 
) the document keeps it’s version history.
Other useful task is the Document Library that allows you to use the already defined custom fields (the metadata) of the document library where the document resides. You can use this fields for creating business rules in the process, filling out forms or send them to other third party systems using Web Services. A field list from the document library will look like the figure on the right.
This kind of integration will provide the most benefit to any SharePoint installation and also, to any Procx installation, letting you master and coordinate your company processes altogether.