You could work in the fullscreen mode (press the F key) which allows panning of the document regardless of size.
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You can use the overscroll feature and it will let you pan when zoomed out enough to see the brims of the canvas. How to find it:
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I cannot believe that I've been using Photoshop for over 12 years, and I've never known about the OVERSCROLL option.
I always got frustrated, hit F, moved it around, hit TAB, hit F, panned it, hit TAB... etc.
This answer from 2012 is just what I needed.
Well it wasn't always that way.
The actual Overscroll preference only became available in photoshop cc 2014, a mere 4 years ago.
Before that there were a few adobe provided plugins/reg edit entries available , but not widely known about or used.