Adobe pdf's embedded into Excel as inserted objects best practice?

Once embedded, they seem to fail upon execution, usually only half of the pdf is available. Error message is: "There was a problem reading this document (14)."

A clue may be that after first opening the Excel workbook, the first pdf always works well, but after one or two, they start failing even though the first ones have been closed and this suggests to me that it may be a "tray" issue. If I save the excel sheet it seems to help (tray?) and if I close the workbook, it seems to help. I can't get anyone at Adobe to deal with me because the help line to to a foreign country and they are not trained in Excel and very quickly blame the case on excel to avoid embarrassment. Does anyone know how to get these two programs to work together better and are there larger trays or maybe trays specifically made to work better with Excel? Thanks!