The only work- around I have found is that I don't use the send feature for estimates and POs direct out of Quickbooks.

I know in Chrome... when I go to print and get a pop- up screen to print, I go to "Open PDF and Preview" and I can use the edit feature in preview to insert a white box over the signature blocks and then Save/Export the PDF from preview.

I know it is not ideal, but it does work and only takes an extra 60 seconds to make the edit, save, download, and upload into an e-mail to the customer/vendor.