I recommend Paint.NET with the Seamless Helper Plugin (direct download). After installation of Paint.NET, you need to copy that DLL file to C:\Program Files\paint.net\Effects\SeamlessHelper.dll.
Here's how easy it is:
Create a new picture with even pixel length. I use 200x200 px here.
Draw something on the center horizontal and vertical lines, like so:
Digital Signing PDF or document using just image is not the best option for non-repudiation. You may use Digital Signature Certificate issued by Certifying Authority in USB Token or Smartcard to Digitally Sign PDF from browser using user's USB Token.
You need to use Browser Extension on the browser side to achieve the same.
The working sample may be ...
This looks like an ideal task for Inscape.
It is free, GPL 2.
It runs on Linux.
It's considerably small, 107 MB download size. That's less than half of Affinity Deisgner, a comparable commercial product. So it should fit on older PCs with little disk space available.
The startup time is certainly not very fast, but once started it's ok. It's a program for ...
So, I searched a bit because this filter looks interesting indeed, and it turns out Gimp has such a filter built-in. Gimp is free, open-source and available for Windows, Mac and Linux.
It is part of the "G'MIC" filter package and called "Polygonize" in the "Artistic" section. I have tried it on Gimp 2.8.22 on Linux. I cannot ...
It depends on what you are trying to do. If you are a digital artist, I can suggest Krita. It's really nice for painting and supports all sorts of pressure sensitive pens but you can just use a mouse or trackpad. I've had a crash or two so I save frequently, but otherwise very well featured. Krita is open source and multi-platform.
If you are using the ...
There are options to produce a painted effect to an image in G'MIC (this can be either standalone or a GIMP plug-in).
Both are free, gratis & open source, and available for Windows, OS-X, Linux and other platforms.
Example of the G'MIC watercolour in action:
You are looking for a Geographic information system.
The Java editor of OpenStreetMap JOSM enables you to edit not only the map of OpenStreetMap, but also your personal (copied or invented) local map. You can invent your imaginary city in an empty map.
You can render your personal map in the OSM format offline.
Examples for fictional maps with OSM technology ...
Since you mention .pages files, I'm assuming your mother runs macOS. Apple's Preview has long had a nifty feature to create, manage, and add signatures to PDF files. Here's how it works.
I'm not sure what "en-masse" entails for you, but you can—pretty easily—add signatures to a bunch of documents by:
opening all documents in Preview;
inserting a ...