The A4 size
The size of the A4 pages are not accurate. Normal size is 11.0x8.3 inches. Also since printers don't print all the way to the edge the documents go out of whack to try to adjust. I'm making a theatrical program for a school project and have had to get very creative with my solutions, wasting a lot of paper in the process.
Rob Wood commented
A4 is a metric size of 297x210mm. I don't get any issues with it on InDesign. The dimensions that you mention are US Letter size.