Instead of being able to click the add row button to a revision table, the table is not editable from Edit Sheet and I can only change it as if it were a sketch from Edit Sheet Format. In doing this, the table is comprised of sketch lines making up the boxes with text boxes as the text. I tried switching between layers to no avail. I am also able to add a revision table to the sheet like one would normally do and it comes up over the current one.
It may be of interest that this drawing is fairly old and was pulled from a database. I am not the original creator. To my knowledge, PDM was never used.