First, a preface for the Adobe folks: I had been going to my banking websites (I have more than one) and clicking on their button to download my monthly statement in PDF format. My IE11 browser always offers me the choice to Open, or Save, or Save As. Habitually, each month I select Open so I can first view the document then, in the Adobe reader itself, I click File then Save As. Once I click the final button to actually save it, is when the Error 21 pop-up appears. I noticed that I have no problem when doing the same thing today from another online bank, or from online websites that are not banks. I felt I had isolated the problem to just one certain online bank.