Finally at Adobe forums a guy with an alias WRFan posted a solution to this long pending bug in Adobe Acrobat 7.

Description of the problem: Running Adobe Acrobat 7.0.0 and the Edit/Preferences/General/Enable text selection for the Hand Tool is selected grayed out. The consequence of this is that instead of effectively using the hand tool users end up accidentaly entering the text edit mode and altering text of the PDF. This is a huge problems for electronic publishing and electronic proofing of publications before print as it can introduce last stage errors in addition to making life miserable for those working with Acrobat 7 for hours on a daily basis.

Solution: Start registry editor. Go to HKEY_CURRENT_USER\Software\Adobe\Adobe Acrobat\7.0\Selection and set the value of bShowKeyboardSelectionCursor and bHandSelects to 0 as shown in the screenshot. Restart Acrobat.