I'm not sure how much detail you need, so I'll start off simple and you can let me know if this got you what you wanted.

1. Create a new report using the wizard and choose those two tables as your datasoure.
2. On the Links tab, make sure they are linked by Invoice_No.
3. On the Fields tab, select the fields you want to print.
4. Click Finish to end the wizard.
5. In the report designer you now have a decent looking report. Move things around and format the fields to make them look the way you want.

Get all that working first.
6. Now, to make each invoice print on a new page, Right-click on the gray area to the left of the Report Footer section and choose Section Expert.
7. Click on the option New Page After.
8. Close the expert and preview the report.

Each invoice should now be printing on a new page.

no formula needed. just click the checkbox. it forces a new page after each invoice automatically.

there can be a extra blank page at the very end, so to prevent that enter a formula of

Not OnLastpage

and that prevents it from happening.