I know this was asked 2 years ago, but I have just experienced the same issue, and in my case it had nothing to do with using the free Community edition as mine was only 3 pages max.

The issue for me was that I had to assign the converter.Options.WebPageHeight to a non-zero value. O is the default, but this cannot be used if your page contains specific components (e.g. frames).

My estimations of the WebPageHeight (in pixels) had become too small over time as I added content but had not updated this value. The result was truncated content in the converted PDF

Updating this field with an appropriate value fixed this issue for me