Paper input size in InDesign not right

When we export a3 drawings to pdf layout does not export the page but contents only, which givecerratic paperzizes in the output. When imported into indesign the imported pages are way off size, often too wide. Is this a setting or a bug.

How big does Acrobat say the paper is?

A3, perfectly. After a lot of experimenting we found out the default settings in indesign were the culprit. As usual. Problem solved.
Now we just hope Layout will get a large boost in usability, because there is a lot te be gained still.