I typically move/reverse each page - don't use the mirror command.
Go to Options/Visible Items and select the "Display Everything" button.
Move/Reverse and select everything using the mouse to draw a box around all the items
Pick the direction you want to flip the drawings.
Repeat for each drawing.
You may have to repair a few items such as roofs and ceilings.
If you are using casement windows remember that they will not reverse operators. Check you exterior doors for the correct Product Codes. Symbols that have "handing because they will reverse visually you will need to update the symbol if your product name refer to handing like tubs. So if you originally had a Maax TSEA LEFT the reversed drawing will visually show as a right hand tub but the label would still show the left hand tub.
Don't forget to turn off the "Display Everything" for all pages