InDesign Page Sizing

 

This is in two parts:

First when you open a new document you set up the page:

A new page defaults to:

w = 210mm, which is also 590 pixels, or 595.276pt.
height - is 297mm, which is also 890 pixels, or 841.89pt.

The margins all round are:

12.7mm or 48 pixels, or 36pt.

Page Size is usually A4, unless it is a flier which is then a Custom Size of 99mm x 210mm.

Then you need to decide on whether you need columns, or just a centre of page grid. Both are shown in the InDesign document but do not print.

The Layout Grids are worked out to the page layout. See the link - Page Layout.

Add a Page when you have started a new document.

File, Document Setup and increase the number of pages.

When you start anew document of two pages, Illustrator assumes you want them two up, which ultimately prints them two on a page. To turn off this option, select File/Document Setup and unpick the facing pages box. A single page up then appears.