Working in DP 5.1.51.2153 for Windows…
When in a dialog like Engraving Options, some of the categories on the left have many pages of options on the right. When my mouse focus is on the right panel of this dialog, the standard PgUp/PgDn keys do not move that window up and down. Oddly, those keys are still focused on the document window. Instead, I have to press and hold the Up/Down arrows, or grab the scroll bar and move it, or use the mouse wheel - all of which are slower than simply utilizing PgUp/PgDn.