I thought of titling this small information tip, YAQADPSTWT (yet another quick and dirty Photoshop transparent watermark tutorial)
That was far too grand a title for what is, in reality, just a quick and easy to apply tip. I hear a lot of talk about watermarking images and I use one simple method to achieve that objective, which is to indelibly mark an image so that anyone wanting to remove your mark will find it much more trouble than it is worth.
This is a simple technique that is intended to be used by anyone who can use Photoshop at any level from tyro to guru.
1. open your image in Photoshop
2. select text tool and type whatever you wish (in black or white text) in any font
3. select tool to move text to where you want it to be and resize if required
4. menu bar > layer > rasterize > type
5. menu bar > filter > stylize > emboss (try a value of around 3 pixels)
6. layers palette (the type layer is already selected)
7. blend mode drop down menu > select hard light
8. flatten image.
You can move the text block at any time until after you have flattened your image. The attached image shows that you can make the text as large and as ugly as you choose (I know... I know... this is a particularly horrific example but it was produced to make the point) and you can rotate it with the free transform command. Common sense dictates that you should make an action out of these steps... I use one for each image size and orientation that I offer.
tah dah! 
The issue of whether one should watermark an image is beset by many shades of opinion. I choose to complete all of my image metadata these days and only post 72ppi images to web sites. This way the image will break up if printing is attempted beyond the pixel size posted. I no longer watermark my images but I accept that many people will want to do this. My preferred method for giving a client proof files to assess is to convert them into PDF files that I can prevent being printed and I lock them with a password so that any unauthorised alteration to the file cannot be carried out. I send all of my work to print houses as PDF files so that the print house cannot adjust them either. YMMV 
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