[Zubersoft]

The PDF libraries are single threaded, meaning access is locked both for opening and closing. So there is no benefit to trying to parallelize opening/closing unfortunately. Having said that, almost operations involving the PDF library are already done on a background thread. I take every measure I can to avoid tying up the UI thread in any way.

Thanks for all your feedback though. Problems you can't reproduce yourself are always the hardest to solve.

Mike