Created attachment 102959 [details] picture copied from adobe pdf and coverted to png so you can see the horizontal banding. I did not provide a full calendar export becuase the PDF is very large (~20MB) I tried the create calendar option (never used it before). I had an issue when exporting to adobe PDF (using Adobe's Printer in Windows)and exporting to OneNote as another test. However I was able to print to a normal printer without issues. The problem was when using the default resolution setting of "high" it results in images that have horizontal lines over them. If I use the "low" setting it is okay and I do not see the lines. I ran 2 tests outputting to Adobe PDF and to OneNote2013 and got similar (but not exact results). I also printed to a normal printer and it was okay. This is on Windows 7, 64bit version of digikam, test version of 5.4.0 (12/23/2016) Example provided.
The compnent used to print is Qt5::PrintSupport. There is no PDF export code in digiKam. We pass data to print to Qt interface which re-route to right printer. As it work with real printer driver, it must work with virtual one too. there is no difference from digiKam side about printing. So, i suspect a Qt5 bug or a problem with your virtual driver. Gilles Caulier
Geoff, The 6.1.0 pre-release installer have been updated this morning. Please test and report to see if you can reproduce the dysfunction: https://files.kde.org/digikam/ Gilles Caulier
I tried this today on Windows 10 Digikam 6.1 release. It now works as expected.