Problem:
When printing a scanned document from Acrobat Reader to the Win2PDF Printer, extra lines appear in the PDF.

Solution:
Turning off the Acrobat Reader "Smooth Images" display preference fixes the issue. To do this, select "Preferences" from the Acrobat Reader "Edit" menu:

In the "Page Display" category, uncheck the "Smooth Images" option under "Rendering".

You will need to close and reopen Adobe Reader for the changes to take effect.