First, though, a bit about watermarks. As the wikipedia article on the topic tells us "[a] watermark is a recognizable image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light (or when viewed by reflected light, atop a dark background), caused by thickness or density variations in the paper."
Watermarks proper are actually added into the paper itself during manufacture, and the text was later printed over the watermark. With the advent of modern computer printing, however, it has become possible to print "watermarks"--actually it might be better to refer to these as pseudo-watermarks--onto standard, clean paper and so to add them, page by page, to a document. This is the sort of watermarking I will be discussing.
This pseudo-watermarking might be added to a document for a number of reasons: a background image--such as a business logo--might be wanted in a document; a copyright notice might be added to a document in this way; or a document might need to be identified as a draft, as opposed to a final revision. The latter of these scenarios applied to me and was why I wanted to learn how to do pseudo-watermarking.
I was pretty certain I could readily find instructions for how this is done using LibreOffice, and a quick search proved my supposition correct. That search furthermore proved that it is a fairly trivial task, so long as one feels comfortable with using some image editing or creating software. I used GIMP for creating my image, though I decided as well to experiment with LibreOffice Draw and had success with it as well. The image created is simply selected as a background for the document. The steps I used were as follows.
First, open GIMP and select File > New. In the resulting dialog, I changed the increments for image size to inches, so as to create an image that will fit within an 8.5x11 inch sheet.
The somewhat tricky part after having done that was to rotate the text such that it would run across the page at an angle. This I accomplished by selecting Layer > Transform > Arbitrary Rotation. Doing this raises a window with a slider that allows you to rotate the image to the desired angle--in my case -57.66 degrees. As will be evident in the screenshot, the text can be better centered in the image using this dialog as well (x and y axes).
Thus, the final product (not very well centered here):
I exported that image to a .png file as the final step. From here, it's a simple matter of opening your LibreOffice document and clicking on Format > Page, selecting the "Background" tab, selecting "Graphic" from the "As" drop-down menu, and finding and selecting the file you just created using GIMP. Once that's done, all pages in that file will have a pseudo-watermark with the text "Draft" on them.
The initial video I found described making the watermark using LibreOffice's Draw program, so I decided I should have a try with it as well. That process was almost as simple as GIMP's, but it had the limitation that the largest font size I could select was 96 point--a bit on the small side. I will nonetheless outline the steps here.
First, I opened up Draw and selected the "T" (for text insertion) from the toolbar at the bottom of the page.
Next, I selected a light gray font color and the largest possible font size from the menu, and printed the text "Draft" in the page. The text ends up being in a horizontal orientation, of course, as can be seen in the screenshot.
In order to make the text run at an angle across the page, it is next necessary to choose the "Effects" tool from the bottom toolbar (the symbol has two blue boxes off kilter from one another and is situated fourth from the right side on my toolbar). Once that's done the highlights of the text box just created turn red, and if the cursor is moved over the top right corner of that text box, the box can be dragged such that it is oriented on the page at the desired angle.
Once the text box is satisfactorily oriented and centered, the file can be exported. Once again, I chose the .png format. The resulting image can then be added to the background of a document using the same process followed above to add the GIMP image.
Finally, though I did not try out this last method, I wanted to see how difficult or easy it might be, using TeX/LaTex, to add a pseudo-watermark to a document. I easily found some directions here. That author describes three different methods, the simplest of which--since it is one on which pdflatex can be run directly, is quite easy with use of the graphicx, eso-pic, and type1cm packages, as demonstrated in the code below:
Here's how the resulting page looks:
That's it for this installment.