We are using Sitecore 9.0.2 & SXA 1.7.1 and we are creating pages using Page Designs.
How do we reuse a Page Design in SXA since a Page Design is linked to Partial designs and these partial design have datasources associated to it that may be local or global
And does that mean that we have to create a new Page Design and Partial designs for each new page?
If your partial design includes components with datasources that should be altered in pages, those components should not be in the partial design.
If you have sets of components that you want to reuse over pages (and alter the datasources if needed), you can use snippets.
There is a question https://sitecore.stackexchange.com/a/10941/237 here that describes the differences between partial designs and snippets.
In your case, I think you have added too much components to the partial design. Keep a (few) placeholders in the partial(s) to give your editors the ability to add components -or snippets- on pages.
Page designs should be set as defaults per template. So when you create a page of a certain template, the assigned page design is set for that page. Normally you have fewer page designs than templates.
