We have the java version of pd4ml and it can render 100 pdfs in about 4 seconds. The .Net version is not even close to being that fast. Has anybody had the same experience?

We never noticed any significant performance difference between Java and .NET PD4ML implementations. Most probably your HTML documents have some structures, whose rendering has been optimized in the recent Java versions: as you may see the actual .NET version is quite older than the most recent Java version.

Currently we've been working hard on the version synchronization and we plan to release a .NET port of v380 in about one week. Hopefully it will resolve the issue you faced with.