By default, all text gets added at a size appropriate to the drawing’s current zoom level. However, when you want to export your work, the various text sizes may not be ideal for a final presentation.
There are two ways to “fix” this issue.
Set the text size to never change. Under the Annotate Tool, select "Colors an Styles" to adjust how all the text will appear on the drawing.
Once you are ready to send out / show your work – change all at once.
The video below shows how to select all text and make them all a single appropriate size.