To print a scrollable pdf

Use a recent version of the Bullzip printer driver

Adjust all column widths
Click + to "Zoom in" and - to "Zoom out" until the Gantt chart fits the available space
Display the application window in Restore mode, and increase the width (or reduce the height) until File > Print Preview shows "Page 1 of 1".

File >
    Print >
       Select the Bullzip PDF printer
           [Properties]
               Layout
                   Orientation = Landscape
                   [Advanced]
                      Paper Size: = A1
                      [OK]
                [OK]
           [OK]
Bullzip PDF Printer - Create File
    General
         Click on the "File Name:  [...] button to adjust directory and enter or correct the file name
        [Save]
    Document
       Quality = Prepress
       Initial zoom level = 50 (E.g. to print up to 49 tasks at a font size of 20, on A1 )
       [Save]