Sounds like this would indicate that it might be an image flattening issue with your computer. Depending on the size of your sheets and the viewports you’ve included in your set, there could be a lot to process.. especially with raster images or viewports that have been changed to “Raster” as opposed to hybrid or vector.
- Try re-adjusting your viewports if needed.. if they are black and white, and no shading is included, then Hybrid or Vector could save some processing power
- Change your PDF Export Options.. knock down the output resolution to Medium, Compress your JPEGs, and uncheck the Create PDF Layers from LayOut Layers. These should trim down some size
If that fails, you could look at compressing your PDF via Acrobat Pro or another free online service. This will cut the size of the file but retain the image and document quality.
Some printers tend to get overloaded if there are lots of layers in your PDF and they’re all set to maximum size and resolution.
Hope this helps!