US Letter vs A4 and Problems with Pagination

[Cal25352091xqkl]

I am copy editing a 300-page book. The author is in Europe; I am in Canada. The original manuscript is written in US Letter size in MS Word.  I have saved it as a PDF and sent it to the author in Europe. It appears that Acrobat automatically converts it to A4 size when he opens it in Europe. This slight change in the document size pushes text to the next page, with a domino effect on the pagination, i.e.,  the pages listed in the table of contents and the index do not correspond with the actual information in the body of the book in most cases when the PDF is opened in Europe. Saving the PDF as an A4 presumably would have a similar effect for the North American reader. Is there a solution?

[Document Geek]

I've never heard of Acrobat automatically changing page size, nor having text reflow in a PDF. I don't know that it even has that capability.

Can you post a screenshot of the page size in the word document, as well as the page size of the PDF from your US version of Acrobat? If you hover over the lower left hand corner of the document, it will display the page size.

We need to pinpoint what the page size is in each program, so that we can ascertain where the change is taking place.

[JR Boulay]

"This slight change in the document size pushes text to the next page, with a domino effect on the pagination, i.e., the pages listed in the table of contents and the index do not correspond with the actual information in the body of the book"

It is the Word document that has been modified to A4 and then converted to another PDF.
This cannot happen with a PDF document.
In a PDF document you can change the US Letter size to A4 (and vice-versa) with Acrobat Pro but it only changes the size of the margins, not the content.