ScanTailor is better than Acrobat and Abby Fine Reader
One major challenge to convert phsyical books to ebooks is the cleaning up of the black marks on margines left from the scanning process.
There are many tools out there that can help to reduce the problem. But, almost all of them have a problem of removing the shades or black marks fully. That is where ScanTailor, a free software for mac and windows, excels.
ScanTailoer is the most valuable pieces of software to turn junked, dirty scanned pages into neat, readable pdf files. Even the most expensive software such as Acrobat Adobe and Abby Fine reader cannot compare with it. It has some magic to clean out all the marks, shades and black marks on the margins of the pages.
Once you process the images in ScanTailor, and OCR them with Adobe or Abby, you get an industry standard pdf files. If you have an old book that you want to convert it to ebook format and sell it, this is the right step to follow.
Scan it with any scanner to image files such as Tiff or PNG–>clean it up in ScanTailor –>OCR it with Acrobat or Abby. Abby can also export it to Epub and Mobi if you prefer these format.
At end of the process, you will have a neat ebook that you can even sell it online.
DJVU to PDF
If you have a DJVU file you want to convert it searchable pdf file, for the macc, you need Cisdem Document Reader to extract all the pages to images (PNG or TIFF) so that StainTailor can import them. I used to follow a convoluted process of exporting them to pdf then converting them to image because my djvu reader (DjVuLibre) cannot extract all the pages to (PNG or TIFF) image.
This is one of the lessons I learned in the process of experimenting with different tools.
How to install ScanTailor
It is hard to find the mac version of ScanTailor. I have spent many hours trying to compile from the source code, and downloading from Homebrew. The Homebrew is failing to download some dependencies in the latest version of Mac OS. If you are having issues to compile from the source code or install from Hebrew, the best option you have is to to download the Universal version (thankfully the authors have compiled for us. This version seems to lack some features in comparison to the Advanced version. But it works fine for the main functions I described here).