Most of the time when we do Inspections we always find an A/C outdoor unit that is out of Level. The biggest problem this can cause is premature failure of the compressor. The compressor is what pumps the refrigerant thru the unit and gives you cool air. Also being out of level can cause stress on the outdoor units refigerant lines. As with anything in your home the A/C unit or units require regular route maintenance. Check the insulation on the copper line if it is damaged or missing It’s time to add a new piece. Check the unit if it is out of level like you will see in this video then relevel the unit Yes it is ok to to pull up on the unit just try not to get to carried away. Things you can use to relevel the unit are Brick, Dirt, any type of composite material. I would never use any type of wood as this material will rot and could be the next meal for a termite or other Wood Destroying Insect.