Increase contrast in PDF

Question

I am trying to batch increase the contrast of a PDF of 600+ pages. I expected such a function in Acrobat's preflight but haven't found anything.

My online research suggests that the task is impossible within Acrobat and that the pages must be converted to images, treated with Photoshop or the like, and then recombined as a PDF. (A user at Super User SE suggested ImageMagick for a faster workflow.) For a host of reasons, this process is not ideal.

Does anyone know of a way to increase the contrast of multiple PDF pages, preferably within Acrobat? Preflight has a variety of color fixups but, at least to my level of literacy, none seem to do the trick.

Answer 1

You may use Enfocus PitStop Pro (at least 13 version) plugin for Adobe Acrobat. This plugin may apply color curves to the objects on pages. So take a look at the screenshot below and it is intuitively clear how this plugin works. BUT there is one BUT. This is perfect and professional solution BUT at the same time it is the most expensive one. The subscription costs 312€ per an year.

Answer 2

Have a look at NAPS2. It is free, and will import PDF, allows brightness/contrast adjustment, and save back to PDF.