edit multi-page pdf

[Leonatus]

I'm dealing with text recognition, thus having frequently to do with multi-page pdfs. Sometimes, the background of a pdf is dark or the contrast is not sufficient. Luckily, I can edit this in IV, going to "Image"->"Change Colours". But, as far as I can see, the changes made apply only to the current page of the pdf. Should it not be possible to apply the changes to all pages of the pdf?
Any help much appreciated!

[Kuki Dent]

IrfanView's main task is to display images. Every other task like playing audio or video or displaying text or PDF documents is additional and nice to have.
But if you want to alter one of these additional files, you need to use a suitable software.
With IV you need to change the background of each single page of a multipage PDF. Then you need to save this single page. After that you can change the
next page and save this one. This will result in a lot of single PDF-pages.
You may eventually try out LibreOffice Draw, which is also capable of opening PDFs.
Or you try out PDF Exchange Editor, which is free for personal use and can do some OCR tasks.

[Leonatus]

Thank you, I supposed something of that kind! I have PDF Ex change Viewer installed, but IV would have been much more comfortable in the case that it worked as I hoped. I'll also give a try to LibreOffice Draw; I didn't know it works with PDF as well.