Adjust Contrast/Brightness in Multi-Page PDFs?

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tallis

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Hey there. Are there any programs that easily allow one to adjust the brightness and contrast in multi-page pdf files? I know I do it one page at a time in Photoshop, but with a book-length scan, this is not a practical option. Thanks in advance for your help.
 
Strangely, when working with a b/w .pdf, the "Adjust Color" option is greyed out in the Preview menu. Very frustrating.
 
Um, it's because there's no color in black and white pdfs. ;) You have to adjust contrast or brightness only with b/w pdfs.
 
Well, yes, I realize there's no color. The problem is that the brightness/contrast adjustment in Preview as described by the link you posted is hidden in the "Adjust Color" option. If you can successfully adjust the contrast or brightness on a multi page BW pdf and explain how you did it without separating the pages, I'd be really grateful.

Thanks!
 
1. Open the pdf in Preview.
2. Make sure the preview pages are showing
3. Click page one
4. "Select All" (or Command + A), All pages are selected
5. Run any Preview tool/filter and all pages will be affected simultaneously

If your pdf is locked, you will not be able to perform this operation.
 
Again, "adjust color" is still greyed out on all pdf files for me, including the unlocked ones. It works fine on jpegs. Is there some tool or filter set that I'm somehow missing that is controllable from elsewhere than the "adjust color" option?
 
But I have not been able to do it either because that particular menu item (adjust color) is greyed out. Alas
 
Where did the PDF file come from that you're trying to edit? Need more specs about the file in order to help more.
 
The pdf I am trying to convert came from a 600 dpi (48MB total filesize) scan of 9 pages in color. It is an Adobe pdf but also opens in Preview.
 
I just did a test on a pdf I downloaded from the internet, and the Adjust color settings were grayed out. When I grabbed a preview from the right column and dragged it to the desktop (becomes a clipping) I can then edit the color on that file.

I don't think you want to do this for all the rest of the 599 pages, though.

I wonder if the pdf you created from the scan got locked somehow when you ripped it to pdf format? What program did you use to build the pdf?
 
Make sure the files you are creating with the Hp software aren't edit-locked. If you create a file, you should be able to edit it in preview.
 
I don't think edit-locking is the problem. I drew a picture in Gimp, saved as PNG, opened it in Preview, checked that Adjust Color was available (it was), saved as PDF, checked Adjust Color again, and now it was grayed out!

I also tried saving a PDF document as PostScript (via Print) and getting the resulting .ps file back into Preview, and Adjust Color was grayed out then too. And there is no way to edit-lock a PostScript file, is there?

As far as I can tell, Preview simply does not support Color Adjust for PDF.

The solution I found was to save my postscript as a TIFF file (which can take multiple pages) using the same resolution as I scanned it in. Then I could adjust color and finally save as PDF again. However, I found that color adjustments only worked for one page at a time, even though I selected all of them. I think it's a general command thing for TIFF: cropping also works for only one page at a time in the TIFF file when I do exactly the same thing that works for all pages in PDF. No big deal for me in this case, because I only had four pages, but I would like to know if there is a way to color adjust all the pages at once. Of course, I suppose you can do it with ImageMagick or something like that.
 
Okay, so it's more than a year later and this is still a problem.

One more time: is there a simple tool that allows one to adjust the contrast in multi-page .pdfs?

Note that Preview does not do the job, and that I am uninterested in converting .pdf to graphics; I'm dealing with 300+ page files.
 
Hi there,

I had the same problem and here's what worked for me:
  • open the pdf file
  • click file, save as
  • and use the scroll box to convert/save the file in TIFF format
  • now open the TIFF file and "adjust color"

I tried to do select all and change the exposure and contrast at once, but somehow it didn't work for me. My file was only 30 or so pages so I did each one, leaving the adjust color tool box open and clicking on the next one, and then saving all when I was done.

After adjusting the exposure and contrast, I saved the pdf file using the same method.

Hope this helps!
 
Another source I found suggested the ColorSync utility. It worked like a charm for me.

Start the ColorSync program on the Mac,
use the file menu to load the PDF file,
select the filter at the bottom of the screen,
click apply (bottom right),
save file.

The filters are rather limited, but the lightness decrease was what I needed for my document to make it a bit darker.
 
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