how to add page numbers in Pages starting from the fifth page

In your menu Insert > Section Break between page 4 and page 5. Page 5 on is now in a new section.

Make thumbnails visible via View at left of the Toolbar and click page 5.

In the Section tab in the formatting panel at the right click the radio button for Start at: and enter the page number you want to start with.

SG

"This didn't work because the page number options were greyed out. "

Did you UNcheck the "Match previous section" checkbox AND select the "Start at" radio button shown in SGIII's response?

Both these steps are necessary to activate the Page Number setting in the Section format panel.

Regards,

Barry