There is no good solution within Acrobat Pro itself. However, you CAN do the edit if you also have Adobe Illustrator installed.
Open your PDF document in Acrobat Pro. Instead of using TouchUp Text Tool, use the TouchUp Object Tool. Select the line of text you wish to alter, right click and choose Edit Object.
Your line of text should open up in Illustrator. Illustrator will use a substitute font, letting you edit at will. NOTE: you will NOT be able to save your change in the original font. Good news is that Illustrator has a large number of fonts to choose from and you will most likely find one that is very close to the original - good enough for quick edit purposes.
Save your change and exit Illustrator. Your change should be reflected by Adobe Acrobat Pro. Another benefit is that your changed text is now TouchUp Text editable from within Acrobat Pro.
Odd that I found this solution that is almost 2 years old on the exact same day as the last guy. This WAS a real pain in the butt. Thank you for taking the time to post the solution. I too was looking everywhere and this worked like a charm. For those that don't have Illustrator - I will come back and post a solution if I ever find one.
I used to change the font quite easy in Acrobat 2006. But now, I'm using Acrobat X and I'am experiencing same problem.
Try to edit the pdf in Acrobat 2006, maybe that will work.
What in the world do you mean by Acrobat 2006. There is no product or version with that name!
I had same prob unable to change font. After messing around (as you do) I found that going 'Tools' - 'Advanced Editing' - 'Touchup Text Tool' then highlight the text & delete it. Then in the empty space right click & select 'Properties' & choose the font you want to use & then re-type. This worked for me (Acrobat Prof 7). Also in 'Preferences' - 'Touchup' I had the 'Choose Page/Object Editor' set to 'Acobat Elements.exe' (path was in the Acrobat Folder). Hope this works for other people.
I was getting this error a lot with PDFs generated by the Adobe PDF printer device.
After some thought, I looked at the "Printing Preferences" for the PDF printer and noticed an option "Rely on system fonts only; do not use document fonts.". Obviously that prevents embedding of fonts (which reduces file size), but also causes the fonts to be made unique, ie. "Arial+0" rather than "Arial", etc. This prevents the editing, regardless of whether the font is installed or not. Unchecking that option and reprinting the document solved that problem. The TouchUp Tool worked thereafter.
Obviously that solution only applies to PDFs created from that source, but might point people in the right direction for related issues.