The changes package, distributed with TeX Live, allows the user to manually markup changes of text, such as additions, deletions, or replacements. This example customizes the package to show author annotations with avatars. (Here's a more conventional example without the avatars. )
The changes package, distributed with TeX Live, allows the user to manually markup changes of text, such as additions, deletions, or replacements. Changed text is shown in a different colour; deleted text is crossed out. The package allows definition of additional authors and their associated colour. It also allows you to define a markup for authors or annotations. (Here's another customised example using avatars for the author annotations.)
A simple example demonstrating how to use some wiki markup syntax in LaTeX, using wiki.sty from the nicetext bundle. Be careful — not everything works, and some commands may break! See http://mirrors.ctan.org/macros/latex/contrib/nicetext/doc/wikicheat.pdf for a cheat sheet. If you're looking for markdown, check out this example!
Use the psfrag package to replace strings in EPS images, so that they are typeset with the same body font as your LaTeX document. Note that your project needs to be compiled with the LaTeX dvipdf engine. To configure this, after creating a new project, click on the Overleaf menu icon above the file list panel, and make sure the "Compiler" setting is set to "LaTeX". (The sample image is taken from the psfrag package.)
This is an example document to show the use of headers and footers. "Special features" are a fancy header, initially made for a CV template, and a "final footer" which will only appear on the very last page.
The tutorial to go with it is here.