ecobin Loc: Paoli, PA

There are many YouTube videos on this - I'm sure you can find one that fits what you want - I did.

dustywing Loc: North East WI

I googled it when I wanted to make one.
I use a brush can be scaled to any size.
Here is one I watched https://www.youtube.com/watch?v=VdmqI8QmarI

Can't ad a sample her

daddybear Loc: Brunswick, NY

There is a company , Mohawk Paper that watermarks for customers, Disney being one. They also make fine and coated papers among other types. Their copy paper is sold to and marketed under different brand names . Same with their photo papers, Strathmore being one. Photo book makers are a large market for them also.

DeanR.

Copfer Loc: Gillette, Wyoming

👍🏻

Morning Star Loc: West coast, North of the 49th N.

Just curious: Are you talking about a "real" watermark here? As in, a watermark that is embedded in paper and quite visible when you hold up the paper against the light?
This would be prohibitive, even in cost alone, for a hobby photographer.
The "watermark" or signature asked about by OP, is the one that gets printed on the paper, not embedded into it.

Copfer Loc: Gillette, Wyoming

I'm just talking about a signature on the photo. Nothing embedded.

DWU2 Loc: Phoenix Arizona area

There are good tutorials for both signature creation and watermarks on Youtube. In particular, look for videos featuring Matt Kloslowski or Julliane Kost.

amfoto1 Loc: San Jose, Calif. USA

Here is an example of my "watermark":



I use a watermark on all my proofs... almost everything displayed online. Those deliberately partly obscure the image so that they are less likely to be "stolen". (For the same reason I also keep my proofs relatively small... no more than 700 pixels on the long side.) Notice that I use a font colored gray and outlined in white. That works well on almost any image... light, dark, anything in between and any color. Since I still see some images taken and used on Facebook and similar, I figure it's only fair that my watermark should serve as an advertisement (Note: Above example is an old one... that website no longer exists. I just haven't yet gotten around to replacing all of the old ones I have online.... this is one of the problems with watermarks!)

In contrast, here's an example of my digital "signature":



I "sign" every finished image, whether print or digital... except for ones that will be used editorially or commercially (where I instead often get a photo credit).

My "fine art" prints not only get signed digitally similar to above, they also are dated, limited edition numbered, titled and signed in pencil in the margin.

Both watermarks and digital signatures can be created and used the same way.

I start by creating the file, usually with Photoshop, although similar can be done with many different programs. I use a partly transparent font and save it as a PNG file, which allows for a transparent background (JPEGs don't and can't be used). This then can be added to any image.... either manually or automatically.

In the past I used FastStone Image Resizer to quickly and easily add watermarks and signatures to images in large batches. Now I use Lightroom for the batch watermarking (sometimes 100s or even 1000s of images in a batch) and Photoshop with individual finished image signatures. Lightroom will size the watermark to the image. Adding the signature manually and individually to finished images in Photoshop (using "layers") gives me opportunity to change the color, increase or decrease transparency, change the size and position as is most appropriate for any given photo.

In fact, I've gotten so quick at it that I now often just add the individual signatures to finished images by typesetting a new one for each image. That's often less trouble than finding and opening one of the files I created for the purpose earlier, then having to adjust it to the particular image.

OnDSnap Loc: NE New Jersey

If your already in PS and have a tablet ...just create a new blank layer and sign it with the Brush tool in the color of choice, you can then use all the layer do-dads as normal, opacity, modes, FX. Whatever (almost)... Then the transform tool to size it, then move tool to position it. Ya done, took me longer to type this.