Here's a friendly reminder that I still have to remind myself of on occasion:
It's easy to make up a great-looking layout and want to send it off straightaway after proofing to the client, so said client can admire the awesomeness you've created and note any changes desired.
But what if your clients don't happen to have Adobe Acrobat (the paid one—not Acrobat Reader) on their computers? No comments for them!
InDesign CS5 export to PDF dialog boxIn order to meet those clients' needs, you'll need to take the PDF you export from InDesign CS4 or CS5, open it in Acrobat, and turn on commenting. I like to remind myself to do this by leaving on the "View PDF After Exporting" option. This is also good to make sure the software gremlins didn't eat your beautiful layout—which does happen sometimes.
In Acrobat, under the Comments menu, click "Enable for Commenting and Analysis in Adobe Reader," click OK on the warning box, and re-save your file.
Here's a video illustrating the process, from the good folks at Adobe.