move Photo from Library to Documents

Do you want to remove the photo from your Photos library and save it in the Documents folder instead? Or do you want to have a copy to be used in other applications? I am not sure, what you want to achieve.

If you want to remove the photo from Photos and keep it in Documents instead, you may have to use the Export command twice, if the photo has been edited. The export command has two variants:

1. File > Export > Export unmodified Original: This will export the unmodified originals, just as you imported them. You should use this command, if you are planning to delete the photo from Photos. It is essential to save the image in the original quality.
2. File > Export > Export ... photos: This will export a new image file with the adjustments applied. You can select the file format, the resolution (pixel size) and the quality, if you select a format with a lossy compression. Use this command, if you need to control the file size and quality for sharing the image with other applications.

Export the photo, selecting Documents as the destination.

Then delete the photo from your Photos library.