How do I "Copy selected text into Highlight... comment pop-ups" box. Using Acrobat 8, Reader 9, shared review.

For Acrobat (8, 9, & X) but not for Adobe Reader you can configure Acrobat Preferences such that selected or encircled text is directly copied into the pop-up for some annotations.

Edit > Prefernces > Commenting category > in the Making Comments pane > tick either / both:

--| Copy encircled text into Drawing comment pop-ups.

--| Copy selected text into Highlight, Cross-Out, and Underline comment pop-ups.

While Adobe Reader X provides the Sticky Note and the Highlight annotations "out-of-the-box" this is not the case for Adobe Reader 9 (or 8).
To use Comment & Drawing markup on a PDF with Adobe Reader 9 the PDF must have been reader enabled with Adobe Pro (8, 9, X).

Using the Select tool text can be selected and copied into an annotation's open pop-up when the PDF is open in Acrobat.
Using Adobe Reader 9 you have the Select tool; however what is selected cannot be copied and pasted into an annotation's open pop-up unless the PDF has been reader enabled by Acrobat Pro.

Thanks David. So, I can only use the highlight and copy feature in Acrobat, not Reader? I have used it successfully in Acrobat. It would be great to have this feature in both products.