Converting PDF from Acrobat Reader to Preview compatibility

Hi everyone:
I have some PDFs that crash Preview when I try to open them, but they open fine in Acrobat Reader. I'd like to be able to open with Preview, so how can I convert these PDFs so that they will work in Preview? I've tried "save as" a new PDF in acrobat reader, but it doesn't work.

Thanks for all the help! I always learn something new when I post here

I've run into this before and opened a defect on ADC. I lost track of what occurred, but as I recall it's a defect in the Preview application and there is no way that I've ever found around it, especially since there isn't an option for previous version compatibility etc in Acrobat Pro even.