In LO, page size and other stationery parameters are defined in so-called Page styles.
Even with 200+ pages, your document should not be built on more than a handful of page styles. To see them, open Format
>Styles & formatting
or F11
. Select the fourth icon from the left in the tool bar and Applied styles from the drop-down menu at the bottom. The list will then show only the styles used in the document.
The parameters for the remaining page styles may be adjusted by right-clicking on the name and choosing Modify...
.
Don’t forget to change also the paper size in the printer settings, which are independent from the page styles.
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