Here you will find general description about how you can contribute to papermerge project. A more detailed version of this document you can find in online documentation.
Contribute to the project just by fixing text typos. Like tis one. Yes, English is not my native lnguage and I do lots of typoz.
Fixing documentation typos is easiest and fastest way to contribute to the project. Even even if you correct one minor typing mistake I will add you to the list of contributors.
Another way to contribute is open issues. Obviously this means you need to at least run once application and test it.
Find detailed description on how to add language support in documentation