Use the two consecutive words from [Control Word Address] to control displaying/hiding the PDF Viewer and selecting the PDF to display.

Control
When bit 0 is ON, the PDF Viewer is displayed and bit 0 is turned OFF.
When bit 1 is ON, the PDF Viewer is closed and bit 1 is turned OFF.
When bit 0 and bit 1 are ON at the same time, the PDF Viewer is not displayed and both bits are turned OFF.

File Number
The PDF with [No.] in the PDF Viewer settings that matches the value stored here is displayed.