This page has samples of various supported Markdown text formatting options. Markdown is supported in Customer Notes, Internal Notes, Line Item Descriptions, Document Intro, Document Terms, Document Contract and Email Templates. 

It's a fairly straightforward way to get really nicely formatted documents and emails.

Headers

# H1
## H2
### H3
#### H4
##### H5
###### H6

H1

H2

H3

H4

H5

H6

Emphasis

Emphasis, aka italics, with *asterisks* or _underscores_.
Strong emphasis, aka bold, with **asterisks** or __underscores__.
Combined emphasis with **asterisks and _underscores_**.

Emphasis, aka italics, with asterisks or underscores.

Strong emphasis, aka bold, with asterisks or underscores.

Combined emphasis with asterisks and underscores.

Lists

1. First ordered list item
2. Another item
 * Unordered sub-list. 
1. Actual numbers don't matter, just that it's a number
 1. Ordered sub-list
4. And another item. 

 Some text that should be aligned with the above item.

* Unordered list can use asterisks
- Or minuses
+ Or pluses

1. First ordered list item
2. Another item
   • Unordered sub-list.
3. Actual numbers don't matter, just that it's a number
   1. Ordered sub-list
4. And another item. Some text that should be aligned with the above item.

• Unordered list can use asterisks
• Or minuses
• Or pluses

Links

There are two ways to create links.

Format #1: Creating a hyperlink allows you to create custom text which when clicked will go to the URL. If this is being used in an email template, be sure to set the Format to Markdown.

[Click here to go to Google!](https://www.google.com)

Format #2: Full URL's by themselves will be recognized by most modern devices and turned into hyperlinks automatically.

http://www.example.com

Images

Here's our logo (hover to see the title text):

Inline-style: 
![alt text](https://www.estimaterocket.com/images/er-logo.png "Logo Title Text 1")

Html with Size: 
<img src="https://www.estimaterocket.com/images/logos/er-logo.svg" width="87" height="26">

Inline HTML

You can also use raw HTML in your Markdown, and it'll mostly work pretty well.

<span style='font-size: 11px;'>Text that you want this small size.</span> 

<span style="color: #ff0000">Red 10% Discount</span>

<span style='font-size: 26px; color: #ff0000;'> BIG Red 10% Discount</span>

<center>Center this Text</center>

<u>Underline This Text</u>

Text that you want this small size.

Red 10% Discount 

BIG Red 10% Discount

Center this Text

Underline This Text

Horizontal Rule

Three or more...
---
Hyphens

***
Asterisks

___
Underscores

Three or more...

Hyphens

Asterisks

Underscores

Line Breaks

My basic recommendation for learning how line breaks work is to experiment and discover -- hit <Enter> once (i.e., insert one newline), then hit it twice (i.e., insert two newlines), see what happens. You'll soon learn to get what you want. "Markdown Toggle" is your friend.

Here are some things to try out:

Here's a line for us to start with.

This line is separated from the one above by two newlines, so it will be a *separate paragraph*.

This line is also a separate paragraph, but...
This line is only separated by a single newline, so it's a separate line in the *same paragraph*.

Here's a line for us to start with.

This line is separated from the one above by two newlines, so it will be a separate paragraph.

This line is also begins a separate paragraph, but...

This line is only separated by a single newline, so it's a separate line in the same paragraph.

Youtube videos

They can't be added directly but you can add an image with a link to the video like this:

<a href="https://www.youtube.com/watch?feature=player_embedded&v=YOUTUBE_VIDEO_ID_HERE
" target="_blank"><img src="https://img.youtube.com/vi/YOUTUBE_VIDEO_ID_HERE/0.jpg" 
alt="IMAGE ALT TEXT HERE" width="240" height="180" border="10" /></a>

Or, in pure Markdown, but losing the image sizing and border:

[![IMAGE ALT TEXT HERE](https://img.youtube.com/vi/YOUTUBE_VIDEO_ID_HERE/0.jpg)](https://www.youtube.com/watch?v=YOUTUBE_VIDEO_ID_HERE)

This page is mostly thanks to Adam Prichard.