How can I set poster presentation scale in cm ?

I would like to make poster presentation in 90cmX140cm. I have doubt that libre office has default scale units are cm or Inches?

For poster size, set dimensions in Format>Page. Use a specific unit after the number. You have many choices: cm, in, pt or even m, mm, ft, …

To constrain the rulers to a specific unit, right-click on it and choose from the pop-up menu.

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