It would be useful to add in Help for Sheet in Calc, in https://help.libreoffice.org/index.php?title=5.1/Calc/Sheet_3&Language=en-US, on the bottom of Page Order:
Note: In order to have continuous page numbers on PDF export or print with different page styles, such as for different sheet orientation, one can create new Portrait and Landscape page styles with 'First page number' unmarked and use them for all pages except the first one that uses Default page style.
Yep -> NEW
The suggested text is not suitable for Calc page formatting. There is no "First page number" checkbox.
However, one can adjust the header/footer to carry page numbering using page styles.
It will much better to write a full help page tutorial on how to use Page styles for spreadsheets, describing use cases in numbering or page orientation. The page can be listed in the Contents tree, similar to
@Timur Can you provide the contents of this page here (either as comment or a ODT attachment)? Title can be "Using Page Styles in Spreadsheets"...