Counter-clockwise: top of the page moves to the left edge. The opposite of clockwise. You need this when your page currently has its top on the right (rotated CW from correct) and you want to undo that.
Flint has a dedicated CCW button.
When to choose CCW over CW
Look at the thumbnail. Where is the top of the visible content? If it's pointing right, click CCW — that rotates the top back to up. If pointing left, click CW. If pointing down, use 180° (twice CCW, or the 180° preset). If pointing up, the page is already correct.
Apply selectively
Select the pages you want rotated. Click CCW. Save. Pages not in the selection don't rotate.
Common case: landscape PDF you want portrait
Some landscape exports came out wrong and you want them portrait. Select all, click CCW (or CW depending on which way the content faces). Save. The whole document is now portrait with text reading top-to-bottom.
Reset if you go wrong
If you click CCW and it makes things worse, click CW to undo (within the session) or hit 'reset all changes' before saving. Once you save, reverse the rotation in a fresh session.
FAQ
Is 'left' and 'counter-clockwise' the same?
Yes. Top moves to the left edge.
How many CCW clicks equal a full rotation?
Four — 360° brings you back to the start.
Difference between CCW and three CWs?
None. Same result. CCW is just faster.
Save before or after multiple rotations?
After. Do all your rotations in one session, then save once.
One click, top moves left. Rotate counter-clockwise.