I have personally used Post Affiliate Pro for almost 2. While I had some small issues, the customer support team quickly resolved them. The software is pretty affordable and has a lot of excellent features and many, many integrations. We took the advantage of free set-up and integration, which was a very nice gesture from the company.

Qiqqa is by far the strongest solution for research and managing pdf's. Zotero, named as a comparison is weak as it does not allow pdf;s to be loaded into its interface - you need to use a pdf reader, which defeats its whole purpose. With Qiqqa documents in a library can be searched together. It has excellent maps of your libraries. It is not prefect, having a few glitches, but still is the only one of its kind.