I have imported a 40 page Word document into Robohelp 2019. This Word doc was originally in landscape, however the output of RoboHelp is in portrait, resulting in cutting off images and tables.
How can I change the orientation of the page in the output Word or PDF?
Basically you don't as HTML has no concept of portrait or landscape.
If you generate an online output, the images should be find there.
For Word and PDF outputs you need to limit the image size. I have found that if you keep any line with an image within about 7.5 inches on the ruler, it works nicely in Word and PDF>
If that's an issue with your online outputs, you may need two versions of the same image set to different sizes and with tags applied.