Libre office draw is wonderful, it can edit pdf docs at ease. Itβs crazly powerful compared to paint 3d
Online sequence diagrams from code. Used to be good but now lacks functionality and design. Has interactive diagrams which is cool.
draw.io - Online diagramming application
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.
SequenceDiagram.org - Clean and fast online sequence diagram tool using scripting and Drag and Drop
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.