I've seen this asked quite a few times, here is how I do it.

Start with two separate quality ink prints on a FD-258 (roll your own, go to local LEO, etc) take extra precaution to keep your prints inbetween the lines and off any of the text.. will make your job easier later.

Scan your FD-258 cards in to your computer, I scan mine at 1200DPI, Document - black & white, PNG file type.

Once you get both of your FD-258 cards scanned in, open them up in your photo editor. I use Adobe Photoshop

Use the magic wand tool and select the white background, now click Select>Inverse. Press CTRL+X or click Edit>Cut to cut your selection. Press CTRL+N or click File>New.

Now paste your prints, CTRL+V or click Edit>Paste

Look to the lower right pane, it will say Layers and show Background and Layer 1. Layer 1 contains your prints and Background is just a white background. We need a transparent background so click the little lock next to Background to unlock the background. Now press Delete on your keyboard.

You should now see your fingerprints (and all the FD-258 form info) on a checkered background vs white.

Click the selection tool and make a box around just your prints, all of your prints in one large box. Now click Image>Crop

Now use your Eraser and erase the lines between your prints and any text. You want to just have your fingerprints left.. if your prints are over a line or text, you will need to zoom in, reduce the size of the Eraser tool and remove the lines.

Once you get done, download this .PDF of the FD-258 Open this PDF up in your photo editor, in Photoshop this will open with a transparent background. In Photoshop an Import PDF box will pop-up, make sure you select the Resolution to match the resolution your scanned your prints, in this case 1200DPI

Now go back to your fingerprint tab, press CTRL+A or click Select>All, then press CTRL+X or click Edit>Cut.

Go back to the FD-258 tab and press CTRL+V or click Edit>Paste.

This will place your finger prints over the FD-258 card. Click on the newly created layer and click Select>All.

Now click on the Move Tool and drag your prints down so they line up with the FD-258 card. At this point go ahead and print out a test page so see how your prints look, you may need to go back and adjust Brightness, Contrast, Levels, etc. I would recommend printing a test after each adjustment to see how it looks. Compare it to your original Ink FD-258.

Once you're happy with how your prints look you can select Layer 1 and press Delete. You should now have just your prints left in the correct location to fit on a FD-258. Now click on File, Print.

When the Print window pops up, click on Print Settings... change Paper Size to User Defined, 8.0" x 8.0", Portrait, Plain Paper and the Resolution to 1200DPI.

Load a few FD-258 cards in your printer (you can write Top and draw an arrow on a piece of paper and print off a test page to see the correct orientation) in my Brother laser printer I place the FD-258 cards face down, with the fingerprint portion of the card being pulled in first.

Now click print. You may get a pop-up stating the image is larger than the print material, just check Do not show again and click ok.

I do not have to play around with margins or any other settings, my prints come out perfectly centered on FD-258 cards every time.

If you have any questions feel free to ask, these instructions are for Adobe Photoshop but you should be able to use any other halfway decent Photo editing software. I have used GIMP before which is very similar to Photoshop, its free and it can be used on several different operating systems, including GNU/Linux.

Thank you for the information!

@BigWaylon

done

Shameless solicitation for help approved by the mod:

I don't have the equipment or local facility to scan/print cards, I'm looking for someone willing to help me print about 10-12 cards.  I already have one completed in ink.  Please PM me if you're willing/able to help.  Thanks.