I tried first setting it to Acrobat 5 did not work at all.
First, awesome that it worked! Second, it's bewildering, to me, that you had to go lower than Acrobat 5! That just seems astounding! But, then, it's the digital world... who knows what? It is a playing field where people have to experiment... so glad you found a solution!
I wrote my response hastily and neglected to add the importance of keeping a copy of the original file intact... assuming you did so... I hope