Writer - How can I change margin for all pages

How can I change margin for all pages? Every page in my document has a specific margin (generated by OCR). When I tried Format->Page and on page to set up, is valid only for a current page…

Open the style sidepane F11 and click on the fourth icon from left (page styles). How many custom page styles are there? They likely have same name followed by a number. What is the filename extension, .doc(x) or .odt? Tell also your OS and LO version.

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