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TitusBluth - I would be tempted to delete all the EPUB formats where's there's also a PDF original format
Then do conversions as and when I accessed the PDF, but only if the resultant EPUB improves readability - after doing a few you'll be able to judge those that will and those that won't.
PDF conversions that process the text almost invariably result in 'lost in translation' faults, which in technical specs can be very irritating because they can result in wild goose chases - such as trying to find non-existent part numbers.
You might find this gadget useful ==>>
Willus.com's K2pdfopt. And there's a support thread here at MR ==>>
k2pdfopt: optimizes PDFs for viewing on e-readers
BR