Error when merging multiple pdf files into one file in Google Drive - pdf

Question

I used the following code (taken from PDF.CO) to merge multiple pdf files in Google Drive:
/**
* Initial Declaration and References
*/
// Get the active spreadsheet and the active sheet
ss = SpreadsheetApp.getActiveSpreadsheet();
ssid = ss.getId();
// Look in the same folder the sheet exists in. For example, if this template is in
// My Drive, it will return all of the files in My Drive.
var ssparents = DriveApp.getFileById(ssid).getParents();
// Loop through all the files and add the values to the spreadsheet.
var folder = ssparents.next();
/**
* Add PDF.co Menus in Google Spreadsheet
*/
function onOpen() {
var menuItems = [
{name: 'Get All PDF From Current Folder', functionName: 'getPDFFilesFromCurFolder'},
{name: 'Merge PDF URLs Listed In Cell', functionName: 'mergePDFDocuments'}
];
ss.addMenu('PDF.co', menuItems);
}
/**
* Get all PDF files from current folder
*/
function getPDFFilesFromCurFolder() {
var files = folder.getFiles();
var pdfUrlCell = ss.getRange("A4");
var allFileUrls = [];
while (files.hasNext()) {
var file = files.next();
var fileName = file.getName();
if(fileName.endsWith(".pdf")){
// Make File Pulblic accessible with URL so that it can be accessible with external API
var resource = {role: "reader", type: "anyone"};
Drive.Permissions.insert(resource, file.getId());
// Add Url
allFileUrls.push(file.getDownloadUrl());
}
pdfUrlCell.setValue(allFileUrls.join(","));
}
}
function getPDFcoApiKey(){
// Get PDF.co API Key Cell
let pdfCoAPIKeyCell = ss.getRange("B1");
return pdfCoAPIKeyCell.getValue();
}
/**
* Function which merges documents using PDF.co
*/
function mergePDFDocuments() {
// Get Cells for Input/Output
let pdfUrlCell = ss.getRange("A4");
let resultUrlCell = ss.getRange("B4");
let pdfUrl = pdfUrlCell.getValue();
// Prepare Payload
const data = {
"async": true, // As we have large volumn of PDF files, Enabling async mode
"name": "result",
"url": pdfUrl
};
// Prepare Request Options
const options = {
'method' : 'post',
'contentType': 'application/json',
'headers': {
"x-api-key": getPDFcoApiKey()
},
// Convert the JavaScript object to a JSON string.
'payload' : JSON.stringify(data)
};
// Get Response
// https://developers.google.com/apps-script/reference/url-fetch
const resp = UrlFetchApp.fetch('https://api.pdf.co/v1/pdf/merge', options);
// Response Json
const respJson = JSON.parse(resp.getContentText());
if(respJson.error){
console.error(respJson.message);
}
else{
// Job Success Callback
const successCallbackFn = function(){
// Upload file to Google Drive
uploadFile(respJson.url);
// Update Cell with result URL
resultUrlCell.setValue(respJson.url);
}
// Check PDF.co Job Status
checkPDFcoJobStatus(respJson.jobId, successCallbackFn);
}
}
/**
* Checks PDF.co Job Status
*/
function checkPDFcoJobStatus(jobId, successCallbackFn){
// Prepare Payload
const data = {
"jobid": jobId
};
// Prepare Request Options
const options = {
'method' : 'post',
'contentType': 'application/json',
'headers': {
"x-api-key": getPDFcoApiKey()
},
// Convert the JavaScript object to a JSON string.
'payload' : JSON.stringify(data)
};
// Get Response
// https://developers.google.com/apps-script/reference/url-fetch
const resp = UrlFetchApp.fetch('https://api.pdf.co/v1/job/check', options);
// Response Json
const respJson = JSON.parse(resp.getContentText());
if(respJson.status === "working"){
// Pause for 3 seconds
Utilities.sleep(3 * 1000);
// And check Job again
checkPDFcoJobStatus(jobId, successCallbackFn);
}
else if(respJson.status == "success"){
// Invoke Success Callback Function
successCallbackFn();
}
else {
console.error(`Job Failed with status ${respJson.status}`);
}
}
/**
* Save file URL to specific location
*/
function uploadFile(fileUrl) {
var fileContent = UrlFetchApp.fetch(fileUrl).getBlob();
folder.createFile(fileContent);
}
It runs perfectly the first time, but then gives an error:
Exception: Request failed for https://api.pdf.co returned code 402. Truncated server response: {"status":"error","errorCode":402,"error":true,"message":"Not enough credits, subscription expired or metered use is not allowed. Please review cre... (use muteHttpExceptions option to examine full response).