Documents and blogs are unique in that they an exclusive feature, allowing you to save your post as a draft before publishing.
Save Draft
- Create a new document or blog post
- Once done editing scroll to the bottom of the page and select Save Draft.
Locating Saved Drafts
- Under the profile, drop-down select Your Content
Drafts - select the draft you wish to work on. 
- From here you can publish your post or continue to edit.
Collaborating on Drafts
You can collaborate on drafts of blog posts or documents. Create the post and save it as a draft. From there, click Share. Select the people you want to share the post with and click Share. The recipient(s) will be able to edit the post and either save it as a draft or publish it.