Plot frames define the page size and page alignment of the schematic pages. They also determine the title block, the grid, and the breakdown of the schematic page in the path and positioning areas (columns and rows).
When carrying out a change of standards, you can adjust the project pages to a different plot frame. The project pages can thus be displayed in portrait and landscape format.
See also
Rotated Pages / Non-rotated Pages
Replacing Plot Frames, Forms, and Function Definition Libraries (Changing Standards)