I am using AngularJs with a REST API. I don\'t have the hand on the REST API. I can store digital object with the API by sending a REST request. I can get it also with a GET req
I think you could using blob, something like
var content=...the content of your request;
var mypdf = new Blob(content, {type : 'application/pdf'});
and check answer from "panzi" in this other question Using HTML5/Javascript to generate and save a file
(One character per element in the array seem pretty nice binary. Probably you don't need to transform it. https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Sending_and_Receiving_Binary_Data )