Hello ralileo,
Welcome to Apple Support Communities.
It sounds like you are attempting to reduce the size of PDF you are scanning through your iPhone and importing to office documents sizes, correct? We're here to help you take a look in to that!
You are able to scan a document using the Notes app on an iPhone and using Pages on a Mac to adjust files sizes. Here are articles on steps to following:
How to scan documents on your iPhone, iPad, or iPod touch using the Notes app
Reduce a document’s file size in Pages on Mac
If you would like to achieve this mainly on the iPhone, checking for third party apps via the App Store might give you the options you are requiring:
Download apps and games from the App Store
The ability to reduce PDF size on an iPhone, would be Product Feedback we would encourage you to give to Apple:
Product Feedback
Hopefully this helps!