The menu item Page Monitor > Show Monitor will open a window that can be left open and which shows info about the current (front) document or tab.

You can customize what you see in the monitor.

• Sizes can be in inches, mm, points (including more than one), and default to Acrobat’s current units from Preferences
• You can choose sizes with high precision (more decimal places than Acrobat) or the same precision as Acrobat.
• You can choose to see the file’s full path
• You can choose to see whether files include comments/form fields

You can also choose to show the Page Monitor every time Acrobat starts (when the first document opens).  You can change options from the Page Monitor menu, or by right clicking on the monitor.

This example shows a file with multiple page sizes:

The window will automatically resize and includes information on bleed if it is present

Page monitor enhancements (6.0)

The page monitor shows page sizes and bleed-related information. Use the Monitor button on the control panel, or Page Monitor > Start monitor in the menu.

 The following enhancements have been made.

• The Page monitor now shows the bleed margin, as well as the  bleed box size
• Right click on the monitor, to Copy page size report to clipboard
• The page monitor now shows page scale (UserUnit) information and scaled sizes