Well, within an open document, the resize to content section of the dialog should stay open, so you wouldn't need to click the plus sign every time. But I can't think of any shortcut to that routine, in general.
I see that in Document Properties > "Resize to content", the "z" is underlined, which I think means that's a Windows key shortcut. And then the button "Resize page to drawing" the "R" is underlined. So it might be possible to reduce it all to key shortcuts.
I'm not sure how to use Windows key shortcuts. After you use Ctrl + Shift + d to open Doc Props, I'm not sure how to activate the Windows shortcut "z" after that.
Oh! Just messing around. Alt + z expands the plus sign. Then.... Yes, Alt + r activates the button. So this key sequence works:
Ctrl + Shift + d, then Alt + z, then Alt + r, then whatever closes a dialog.... Alt + c (Or leave the dialog open - due to a bug, it opens on the edge of the screen anyway.)
Other than that, I can't think of any faster way.