The above is what recipients see on the back of my cards. This is how I add my own personal "Made by..." information. You can always order and buy a personalized stamp, but I like my digital one. It's easily changed at any time (you can even add an image if you like), and since I've centered it in the file, there's no pre-stamp "Am-I-lined-up?-don't want-to-ruin-my-card-blank" anxiety; when it prints it's right where I want it to be. Oh, and no stamping ink goof worries either.
It does take more time to set up initially, as you need one file for each card size you use, but after that you're good to go.
These instructions assume good working knowledge of digital imaging software. Consider them general instructions to inspire you and get you started. I can't give specific details as each image processing program is different; adapt these to whatever software you use (I use four different programs, I haven't found one yet that does everything just as I like).
1. Create a computer file with a digital canvas/base image the size of your card. I prefer using centimeters as my measurement size; they're more precise. For example, a 13.5 cm square card will be a canvas with a width 13.5 cm and a height of 27 cm. It will look something like this (white portion only):
2. Choose your font(s) and type face size and type your "Made by..." information. Your goal here is to create a space that is the width of your card back—in this case 13.5 cm—and make sure that your "Made by..." information is centered in that space. This is for a landscape card and is what you see at the bottom of the above image. Play with it until it looks like what you want.
3. For a portfolio 13.5 cm square card, make sure your ruler display is shown, if it is not already. Copy paste your "Made by..." info as you did in #2 and turn it clockwise. Place it across the first 13.5 cm of the card (use the ruler as your guide). It should look like this:
4. Be sure and save your files in a .png format (or .psd in Photoshop). This will allow you to make changes to your text. I recommend naming your files the card size and whether it is landscape or portfolio so that you can find them easily—i.e. 13.5 cm landscape.
5. Put your card blank in your printer's manual feed and print. I have a Canon MG6150 printer. I place my card blank in the back manual feed, go to my printer options and personalize them for the card blank size I've inserted (this only takes a few seconds). You do need to know exactly how your printer prints. For example, mine reverses what I see on the print preview. If you don't know, experiment first with normal paper cut to your card's size till you understand how your printer works.
6. Think of printing several of your favorite card blank sizes at one time so there's always one on hand in a hurry.
Have fun creating your digital "Made by" stamp!