In Impress: How to default A4 size when printing?

I need to change the default configuration for all new or existing documents in order to print on A4 size. There is a way to configure this in some configuration file?

I need to do this without the interface, just changing properties on a file or registry key. This is because i need to make the change in a lot of computers.

Open a blank document. From the menu, choose Slide>Properties. In the “Page” tab under “Paper Size / Format” you can select “A4”. Make all the settings for your printer, including A4. You should save this modified document as a document template. All new documents will have the new format.

For existing older documents I can offer you no “automatic” solution.

Thank you, but i need some solution to apply unattended to the users.

@Trivium while saving the template as indicated by @Hrbrgr, check the mark to set it as your default template: after that any new document will use that setting without any extra work.