If you haven't already done this, you might ask some of the people who are unable to get the PDF document when using Send Forms, ask them if they are trying to open the document on a cell phone or on their computer. We found that some of our customers were trying on a phone, and the file they get on a phone isn't really a PDF, it's some other kind of weird format.  Some but not all.  Sadly, one of ours that always got jibberish was the Board President of our company's board of directors ... needless to say, the reputation of QB didn't score high on her list!

You can try customer service, but likely they'll lead you down a rabbit hole trying to find errors in your system, the customer's system, sunspots, the "time of the month", the weather in China, or who knows what else????