From Lidka's Articles:

Twelve Tips to building better pages

1. Delete unused master pages and blank pages.
Deleting all unused Master Pages and blank pages from your publication will make your file less complex and therefore smaller in size.

2. Check page geometry.
Always use the measurement palette for positioning. You can use it like a calculator: add, subtract, multiply and divide. There is really no need to eyeball for positioning.

3. Delete unused colors, style sheets and h&js.
To make file sizes smaller, delete all unused colors, style sheets and H&Js from your palettes.

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