Hello,
If you would like to preserve tables, figures, and equations as they are, I think it is better to use programs that converts all content to images and process it later.
There are many programs such as PDFLRF, PaperCrop, PDFread, soPDF, and so on.
I will highly recommend PDFLRF and PaperCrop and this following thread may be of help.
https://www.mobileread.com/forums/showthread.php?t=32360
Have fun with PRS-505