Hello,
This is a small but annoying bug that I noticed in 5.1.0 (it worked well in 4.3.0).
In the "Reorder and Merge Print Jobs" window, the "Merge All" button is active by default. But after using a "Sort" option (for example "Sort by ID ascending"), the "Merge All" is greyed out, and only becomes active after:
- a single click on any print job
- focus on the PDFCreator is lost and then regained (for example by clicking another window, and then PDFCreator again)
Before sorting:
After sorting:
But aside from that I really enjoy this application! 
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