Email PDF from Firebase Storage as attachment using SendGrid - node.js

Question

I've created a Firebase Function that, upon click, will get a PDF from Firebase Storage, attach it to an email and send it via SendGrid.
I have no problem getting the PDF Storage URLs and sending the email, but I'm not able to attach the PDFs. I've tried referencing the SendGrid documentation and it seems like the fs.readFileSync function doesn't work on URLs.
How can I get the data from Firebase to be able to stringify it to base64? I've tried reading the Firebase documentation as well but can't seem to be able to figure out a solution. Any help would be greatly appreciated!
Function that successfully grabs all Document URLs from Firebase Storage
const getDocumentURLs = () => {
firebase
.storage()
.ref("Tenant Resumes/" + tenantID)
.listAll()
.then((res) => {
res.items.forEach((result) => {
result.getDownloadURL().then((docURL) => {
setDocumentData((newURLs) => [...newURLs, docURL]);
console.log(docURL);
});
});
}); };
And the firebase function (the console.log gives an error that says "Not an object" - assuming this is because I'm passing a string URL not an actual file)
exports.sendTenantMail = functions.https.onCall((data, res) => {
const name = data.name;
const email = data.email;
const documents = data.documents;
const documentOne = fs.readFileSync(data.documentOne).toString("base64");
const documentTwo = fs.readFileSync(data.documentTwo).toString("base64");
const documentThree = fs.readFileSync(data.documentThree).toString("base64");
const documentFour = fs.readFileSync(data.documentFour).toString("base64");
const documentFive = fs.readFileSync(data.documentFive).toString("base64");
const documentSix = fs.readFileSync(data.documentSix).toString("base64");
const realtorEmail = data.realtorEmail;
console.log(fs.readFileSync(data.documentOne).toString("base64"));
const msg = {
to: "concierge#chexy.co",
from: "concierge#chexy.co",
templateId: "d-1aec2e98c1af44fdb0e1f97d540c6973",
dynamicTemplateData: {
subject:
"A new tenant resume has been submitted by " +
email +
" for " +
realtorEmail,
name: name,
},
attachments: [
{
content: documentOne,
filename: "Doc1.pdf",
type: "application/pdf",
disposition: "attachment",
},
],
};
sgMail.send(msg).catch((err) => {
console.log(err);
});
});
Any help would be huge!