base64 from API call to Adobe PDF Embed API - ajax

Question

I'm trying to embed a PDF on a web page. The native PDF viewer in Chrome has a size limit of around 2mb, so I'm trying to use Adobe's API (https://www.adobe.io/apis/documentcloud/dcsdk/pdf-embed.html)
Because of the way that a CMS that I'm using stored files, I have a Base64 string to work with.
Using code from https://gist.github.com/kiritodeveloper/06186343e41e21a94411b3987e84c5de, I was able to pass my base64 string to Adobe's API and embed the PDF about 60% of the time in Chrome, but now it doesn't work in Firefox.
I'm using ajax to get to my CMS's API to retrieve the data, but I think that the adobe listener is running before the data is returned; when it does work, it's just chance. How can I get the order right so that this will work? Can I use an asynchronous call to get this data?
const clientID = "ADOBE API KEY HERE";
var queryPath = "$/PDFBase64"
jQuery( document).ready(function() {
var pdfData = '';
getPDF();
function base64ToArrayBuffer(base64) {
var bin = window.atob(base64);
var len = bin.length;
var uInt8Array = new Uint8Array(len);
for (var i = 0; i < len; i++) {
uInt8Array[i] = bin.charCodeAt(i);
}
return uInt8Array.buffer;
}
document.addEventListener("adobe_dc_view_sdk.ready", function () {
var adobeDCView = new AdobeDC.View({
clientId: clientID,
divId: "adobe-dc-view"
});
adobeDCView.previewFile(
{
// convert the Base64 encoded PDF and convert it to an ArrayBuffer
// and pass it as a Promise
content: { promise: Promise.resolve(base64ToArrayBuffer(pdfData)) },
// The filename name to display in the View SDK UI
// and also used as the filename of the PDF when downloaded
metaData: { fileName: "Download.pdf" }
}, {})
});
function getPDF() {
jQuery.ajax("/api/Query?queryname=" + queryPath ,
{
type : "get",
"async":false,
contentType: "application/json",
headers: {"RequestVerificationToken":
document.getElementById("__RequestVerificationToken").value},
success: function(data){
iqa = data.Items.$values;
if(iqa.length>0){
for (var i = 0; i < iqa.length; i++) {
filt = iqa[i].Properties.$values;
pdfData = filt.filter(x => x.Name == "PDF")[0].Value;
};
}
return pdfData;
}, error : function(xhr, textStatus, errorThrown ) {
if (textStatus == 'timeout') {
this.tryCount++;
if (this.tryCount <= this.retryLimit) {
//try again
$.ajax(this);
return;
}
return;
}
if (xhr.status == 500) {
console.log(errorThrown);
} else {
//handle error
}
}
});
};
});