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Hi Darcie,

I believe you have solid hatch with transparency applied to it and you save to PDF with "print transparency" option enabled.

Am I correct?

If yes, then AutoCAD creates raster image for transparency solid hatch in PDF file and Preview app prints such raster images inside PDF files as black areas - it is a bug in Preview app on Mac.

You can try to print from Adobe Reader instead of Preview, or convert PDF to JPEG format before printing from Preview app.