This has become very frustrating . . . I have two documents (52pp), contents identical one landscape the other portrait. I can change the page size in the portrait document but not in landscape. Document set up, page adjust not responding although using page tool can I just the size but it automatically springs back to the original. Obviously something I have done but have spent four hours without success. Running Indesign 2019 under Windows 10. Any input greatly received many thanks in advance.
If you have used the page toool to change pages they will no longer respond to changed settings in Document Setup -- the Page Tool behaves much the same way that applying a manual formatting change to text affects the ability to format using styles.
That might not be your problem, of course, but it may explain what's happeing. If you did not do some sort of wholesale Page Tool adjustment (say to a Master Page), try exporting the file to .idml, open that and resave with a new name, or try moving the pages into a new file you've set up with the correct page setup.
If you want to make changes in the document properties, use the document setup, not the page tool. The page tool is meant for exceptions. If all pages are resized with the page tool, you cannot make global changes on pages anymore.
If you want to make changes with the page tool to a specific page and you want to stick, hold down cmd/ctrl key during size change.
If you want to use page adjustment, take care that all frames align with the border guides and in some cases with ruler guides.
Thank you Peter. Saving as *.idml as suggested but had no effect on this occasion, you mentioned Master Pages. So I changed the orientation of the MP from LS to PT and then reversed back to LS and voila was able to change global page size. Still unsure as to what happened but problem solved. Many thanks regards, Garry
Thank you Willi. Have noted your comments and your suggestions are robust. Cheers, Garry
Glad tohave given you enough info to let you delve deeper to solve the problem.
You may still have some undiscovered issues which might benefit from moving the pages to a new file.