Fixing up scanned PDF files

I recently wanted to scan part of a book, and my lab has a machine that can auto-feed pages and email out a PDF file. Thus, I photocopied the relevant pages from the book, and fed them into the PDF-making machine. The problem is that the process of photocopying the book pages introduced a bunch of ugly black regions around the interesting text, and even that text has a tendency to be off-center and even rotated slightly. I fixed it using a combination of Acrobat Professional, Photoshop, and Illustrator.

Supposedly, Acrobat Professional will let you edit a page as an image directly by selecting the “TouchUp Object” tool from “Tools -> Advanced Editing”, clicking the page of interest, then right-clicking and selecting “Edit Image”. However, for me this results in an error message: “Could not complete your request because a color was specified using an unsupported color space”. My good friend Google told me this is a bug, and that my color spaces are just fine, thank you. So, what to do?

I found this article on Adobe Forums, which proposes an alternative that worked for me. To summarize (actually, to be verbose, the Adobe Forums messages are hard to follow):

In Acrobat, select “Advanced -> Export All Images”. I selected TIFF as the output file format for no particular reason, but it worked. Once the images are all exported, quit Acrobat and fire up Photoshop. Open your new image files (recall that the open dialog box allows you to select multiple files), and fix them up. The pattern I got into which worked pretty quickly was to press Apple-+ to zoom to a comfortable level, select the region I did like, the press Apple-X, Apple-A, Delete, Apple-V. This cuts the interesting portion, selects all the rest, deletes it, then pastes the interesting portion back. It has the additional benefit that the paste operation by default centers the newly pasted object. Then, if rotation is necessary, rotate it using Edit -> Transform -> Rotate (this does the “right thing” because the paste operation created a new layer). Select Layer -> Flatten Image, then Save, and repeat for the other pages.

Once the images are all edited, it’s time to recombine them into the PDF. I used Illustrator to do this, as it has a feature called “Re-link”. Select Window -> Links to display the “Links Palette”. Use it to replace the image on each page with the appropriate TIFF file.

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