@Anonymous ,
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It looks like you have wipeouts in your blocks. Some PDF plotters don't deal with these as expected. Eliminate the wipeouts or consider alternatives.
Sorry, I guess I didn't look close enough. The "trick" is in controlling your content. Dig into those symbols and determine what the objects are and their properties. If that doesn't give you enough to go on, share a small sample file and you will get something more than guesses.
Can't see a thing. Attachments in email responses don't get posted.
Have you tried exploring your content to figure out what you need to do?
I'm assuming enough basic CAD knowledge on your part to figure it out with a bit of guidance.
Figured it out....In Model view, highlight the object, right click and select Block Editor. In the Editor mode, you highlight and delete the blackened area, close the Editor and click Save the changes to DET. All of the objects are now clear and you are able to read the content.