THIS PART IS EDITED
For 'software-generated' PDF-files, i.e. PDF's not created from scans, I recommend to use (and upvote the answer by Krasjet) pdf.tocgen. Using this package becomes even easier with the toc-mode package for (Spac)Emacs described next.
For all other PDF and DJVU documents there is a new package called toc-mode for Emacs, which in my opinion ...
epub have an html format, is possible to insert malware inside. Any antivirus can check your ebooks and report you if some is infected.
By other side, if you bought it from a marketplace as Amazon, probably your ebook is virus free.
If you download it from "other sites"… well, you must assume that "can" be infected, so use any online antivirus to check ...
It depends from what you want to do. If the files should be separated, the best option is to zip them and send the zip file; the buyer will unzip them. Otherwise there are programs which merge many input files. I use PDFsam basic (https://pdfsam.org), but there are many alternatives: check https://alternativeto.net/software/pdfsam/ .
There are three ways you can do this:
You can use Google translate
You won’t be doing this directly.
First, you need to copy the text from the PDF file and paste it on
the google translate.
Once translated, transfer the new converted text to a word document
For PDF format preference: Convert the document file to PDF by clicking File, go to Save as, ...
I wrote an open source command line toolset called pdf.tocgen just for doing this. It uses the embedded font attributes and position information of headings to generate a table of contents automatically.
For example, for the PDF version Paul Graham's On Lisp, available for download on his website but comes without a table of contents. You could use the ...