This is how it can be done in PD13, I expect PD12 will be similar. There are two methods:-

1) Select the clip and you will see a blue circle in the centre in the preview window. Move the cursor over the circle and it will change to two curved arrows. Left click and drag to rotate the frame.

If this doesn't give precise enough control:-

2) Select the clip and click on Power Tools. Check the box for Video Rotation and use the controls to rotate in 1 degree increments.

After rotation you may want to resize the clip slightly to remove black triangles at the corners. This is done by dragging the small white circles around the edge of the preview window. Regards,
Mike

Home-build system:
Intel Core i5 Quad Core 3.3GHz, 2 x 4GB DDR3 1333MHz,
Asus Nvidia GT440 1GB, 2 x Western Digital WD10EARS 1TB, 1 x Seagate ST1000DM010 1TB,
Windows 7 Prof 64-bit, PD 9 Ultra 64, PD 13 Ultimate 64

Thanks for the reply.

One degree corrections are too big for me, unfortunately and, as you implied, the first method doesn't give enough control.

Do later versions of PD offer finer increments?

Thanks.

D. Windows 10Pro x64; i6800k; GTX1070; 64Gb RAM; 256GB and 512GB SSDs; 2 x 4TB Storage:

Well, as I said, I am working with PD13 and that only gives one degree increments. There is only one later version, PD14, and I don't know if that offers finer control but I would doubt it.

I'm surprised that one degree is too coarse an adjustment, though. I doubt whether most people would notice an error that small. Regards,
Mike

Home-build system:
Intel Core i5 Quad Core 3.3GHz, 2 x 4GB DDR3 1333MHz,
Asus Nvidia GT440 1GB, 2 x Western Digital WD10EARS 1TB, 1 x Seagate ST1000DM010 1TB,
Windows 7 Prof 64-bit, PD 9 Ultra 64, PD 13 Ultimate 64

Another option here is to use keyframing. If you highlight the clip and then go to the keyframe "Rotation" option. You'll see it set at 0.00 (I don't know if that is degrees or not) and that can be incremented by a minimum of 0.01 at a time. This is almost indiscernible on my screen.

If you make sure that the position scrubber is set to the start of the clip and set the amount of rotation required. Now right click the keyframe at the end of the clip and choose the option to duplicate previous keyframe. The amount of rotation will now remain the same throughout the clip.

p.s. - Just tried setting the final keyframe to 360.00 and when I previewed it did one full rotation so it is in degrees.