How do I prevent my iPad Pro from automatically returning to the first page when viewing multi-page counted cross stitch charts?

I'm going to go out on a limb here and say you're using the wrong application.

Pages is, predominantly, a text-based application. While it does have support for things like embedded images, tables, charts, etc., that isn't its thing. In this case it sounds like it's getting overwhelmed by the multi-page table and getting in the way of your workflow.

In a very quick and dirty test here, I can replicate your situation - if I click on the page, outside of the table, it jumps back to the first page, but if I click in the table, it stays on screen. Maybe that's enough?

Without seeing the chart (TBH, I've never heard of a counted cross stitch chart before), it's hard to know what to advise. If it's mostly tabular data then I might suggest using Numbers instead since it is inherently table-based (sure, it's a spreadsheet app, but columns and rows are its bread and butter).