1.ESC or ENTER key lets dimension line disappear
2.use CS versions of photoshop to open pdf and select page to edit.see screenshot attached.you may also use number of plugins of photoshop for editing pictures
3.If you want to export embedded image in pdf
Open your file in Photoshop choose page with image(you can also edit ).
Go to File > Export > Export Preferences.
Set your Export preferences, such as format, quality and destination.
Now go to File > Export and select Export As… at the top of the menu to export with your saved preferences.
you can also export with single step in photoshop