Reducing the size of a document or image will depend on the format of the file item. You can use a search engine to research your specific document type.
Please see the instructions below advising how to reduce the size of PDF files on a Mac -
1. Open a PDF document in the Preview app.
2. Click on File in the menu bar at the top of the screen.
3. Click on Export As.
4. Click on the "Format:" drop-down menu.
5. Click on PDF.
6. Click on the "Quartz Filter:" drop-down menu.
7. Select Reduce File Size.
8. Select a location in which to save the PDF.