Scribus - Scribus is a desktop publishing (DTP) application.
draw.io - Online diagramming application
RagTime - RagTime is both a traditional Office and DTP layout application.
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.
Pages - Pages for Mac is a word processor that offers tools needed to create documents.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.