You need to split the relevant parts of the document into Sections - Insert - Break - Section break.
Thus pages 1 - 33 form section 1, then p 34 is section 2, pp35-39 are section 3, p 40 is section 4 etc etc.
For each section you can then set up a different header/footer and then scroll through each section using Show Next/Show Previous.
Any page numbering inserted in the footer will remain in sequence.
The Word pedants will always tell you that a 70 odd page document is too long and you should split them up. I've never found a problem but as ever don't forget to keep a back up or two - just in case.
Hope this helps & good luck