2. A system, comprising: one or more processors; and memory storing instructions that, if executed by the one or more processors, cause the system to: receive user input corresponding to operations on a document, the one or more operations causing a change to an overlay of the document, the overlay containing user annotations to the document; transmit an application programming interface call to upload the overlay for the document having an identifier specified in the application programming interface call; receive, from a document management and collaboration system, a second document identifier corresponding to a version of the document which corresponds to the overlay; receive a request for collaboration on the document; obtain the document and the overlay by transmitting a second application programming interface call that specifies the second document identifier; and transmit the obtained document and the overlay to one or more collaborators for collaboration.
2. A system, comprising: one or more processors; and memory storing instructions that, if executed by the one or more processors, cause the system to: receive user input corresponding to operations on a document, the one or more operations causing a change to an overlay of the document, the overlay containing user annotations to the document; transmit an application programming interface call to upload the overlay for the document having an identifier specified in the application programming interface call; receive, from a document management and collaboration system, a second document identifier corresponding to a version of the document which corresponds to the overlay; receive a request for collaboration on the document; obtain the document and the overlay by transmitting a second application programming interface call that specifies the second document identifier; and transmit the obtained document and the overlay to one or more collaborators for collaboration. 10. The system of claim 2 , wherein the instructions further comprise instructions that, if executed by the one or more processors, cause the system to receive the document in response to a third application programming interface that specifies the document identifier corresponding to the document.