It is a real case, and the author of Turn on Measure Tool in Reader for 25,000 PDF documents has been my customer, he bought my software Batch ReaderEnable, because he has already bought the license of Adobe Acrobat, so he just payed extra USD$39, and he can easily converted 25,000 PDF documents.
And, I’d like to correct something in his requirement,

I work for a city government and I have 25,000 scanned maps as PDF documents. Our users (they have Acrobat Reader(should be Adobe Reader) would like to be able to use the measure tool to measure distances on the maps.
From my research, it seems I need to turn on “Enable Usage Rights in Adobe Reader”(should be “Enable For Commenting and Analysis In Adobe Reader” aka “Reader Enable” and in Adobe Acrobat X Pro, it is called “Enable Commenting & Measuring…” ) in order for that tool to work in Adobe reader. Also from my research, it seems there is no way to automate, or batch process, these action for the 25,000 PDF files. There are some references on the web that LiveCycle can do this(Yes, Adobe LiveCycle can do it, but it is very expensive), but nothing confirmed, and when I called Adobe support they said in face, it was NOT possible to batch “enable usage rights“(“Enable Commenting & Measuring”). At. All. Period.
…

btw, Batch ReaderEnable Updates to Support Adobe Acrobat X Pro

I like use Sumatra PDF, because it is a slim, free, open-source PDF reader for Windows. Portable out of the box. and I just notice it has updated to 1.3 on Feb 04, 2011 with many changes,

* improved text selection and copying. We now mimic the way a browser or Adobe Reader works: just select text with mouse and use Ctrl-C to copy it to a clipboard
* Shift+Left Mouse now scrolls the document, Ctrl+Left mouse still creates a rectangular selection (for copying images)
* ‘c’ shortcut toggles continuous mode
* ‘+’ / ‘*’ on the numeric keyboard now do zoom and rotation
* added toolbar icons for Fit Page and Fit Width and updated the look of toolbar icons
* add support for back/forward mouse buttons for back/forward navigation
* 1.2 introduces a new full screen mode and made it the default full screen mode. Old mode was still available but not easily discoverable. We’ve added View/Presentation menu item for new full screen mode and View/Fullscreen menu item for the old full screen mode, to make it more discoverable
* new, improved installer
* improved zoom performance (zooming to 6400% no longer crashes)
* text find uses less memory
* further printing improvements
* translation updates
* updated to latest mupdf for misc bugfixes and improvements
* use libjpeg-turbo library instead of libjpeg, for faster decoding of some PDFs
* updated openjpeg library to version 1.4 and freetype to version 2.4.4
* fixed 2 integer overflows reported by Stefan Cornelius from Secunia Research

My Batch ReaderEnable software supports batch convert PDF files with one of the following features,

• Enable For Commenting and Analysis In Adobe Reader(aka Reader Enable and called “Enable Commenting & Measuring…” in Adobe Acrobat X Pro)
• Enable TypeWriter Tool in Adobe Reader(aka TypeWriter Enable, called “Enable Adding Text in Document (that are not fillable forms)…” in Adobe Acrobat X Pro
• Enable usage rights for Adobe Reader (aka Usage Rights Enable called “Enable Additional Features…” in Adobe Acrobat X Pro)

btw, Batch ReaderEnable has three editions,

• GUI Version(Window Version)
• Console Version
• Hotfolder Automation/File Monitor/Folder monitor Version, automatically monitor the selected folder(with sub-folder) and convert the new PDF files in the folder

• If want to buy GUI Version and Console Version, please click here, and If you want to Buy Hotfolder version, please visit here.