If you are using a PC (not laptop) open a text layer by clicking on the "type" tool in PS and hold down the alt key and type 0169 using the number pad. This will give you the copyright symbol. Then type what ever else you want . You may choose font as needed.
If you want to have the Copyright/Watermark partially transparent, within the layers palette the Opacity function should do the trick. Scroll the opacity back as much or as little as you want for the layer you choose to get the desired effect.
I have a separate PSD file with different colors and sizes ready to go. Once I'm done with my image, I open the psd file and drop it on top of the image.
You can also make a brush of your signature, and then 'stamp' it onto your images at whatever size you want. Just put your brush over your picture, (might be a good idea to use a new layer) and hit the bracket keys to size it up and down by 10 pixels until its the size you want. The bracket keys are the [ and the ]
To make a brush, get your signature into a black/white digital image (or use black text) and select the black text or signature, then choose EDIT > DEFINE BRUSH, and it will make a brush at those pixel dimensions for you to use whenever you need it!