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The PDF API that saves you time & money
Want to learn more about the API? The interactive playground on this page uses our Native API. Check out the API Documentation for more details.
Generate up to 600 free documents every month with our PDF API. Convert HTML to PDF, PDF to PNG, or merge PDF workflows with ease using simple JavaScript. CustomJS is more affordable than most other PDF APIs and works seamlessly anywhere, including Make.com and n8n.
✅ 600 Free Documents Every Month
💸 Cheaper Than Other PDF APIs
🛠️ No New Servers Needed
Start free with 600 PDFs per month
Or use our standalone PDF API anywhere
A PDF API allows you to create, edit, merge, and convert PDF files automatically—no manual steps required. But most APIs are slow, costly, or overly complex. CustomJS changes that with fast, serverless PDF generation powered by simple JavaScript. Convert HTML to PDF efficiently—saving both time and money.
- Lower Cost: Save money every month with simple, honest pricing.
- Faster Speed: Get your output PDF files instantly without waiting.
- More Flexibility: Build exactly what you want with serverless JavaScript anywhere.
Advanced PDF Features
📦 Using External JavaScript Libraries (QR Codes)
You can use external JavaScript libraries like QRCode.js in your PDF templates. When using ES Modules, wrap your import in a module script tag:
<script type="module">
import QRCode from 'https://cdn.jsdelivr.net/npm/[email protected]/+esm';
// Generate QR code
const qrDataUrl = await QRCode.toDataURL('https://example.com', {
width: 150,
margin: 1
});
// Set the image source
document.getElementById('qr').src = qrDataUrl;
</script>
<img id="qr" alt="QR Code" />⏱️ Async Rendering with window.__RENDER_DONE__
When using asynchronous JavaScript (QR codes, charts, API calls), you must signal when your content is ready by setting window.__RENDER_DONE__ = true. The PDF generator waits for this flag before capturing the page.
<script type="module">
import QRCode from 'https://cdn.jsdelivr.net/npm/[email protected]/+esm';
// Initialize as false
window.__RENDER_DONE__ = false;
async function generateQR() {
// Your async operations
const qrDataUrl = await QRCode.toDataURL('https://example.com');
document.getElementById('qr').src = qrDataUrl;
// Signal that rendering is complete
window.__RENDER_DONE__ = true;
}
// Start generation
if (document.readyState === 'loading') {
document.addEventListener('DOMContentLoaded', generateQR);
} else {
generateQR();
}
</script> ⚠️ Important: Without setting window.__RENDER_DONE__ = true, your PDF may be blank or incomplete because the generator won't wait for async operations to finish!
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Use other examples to quickly create and work with PDFs
Quickly create, merge, compress, and convert files with our ready-to-use PDF API endpoints. Build your own PDF generation API that fits your needs.
- PDF to PNG – Turn PDF pages into png images. View preset
- PDF to Text – Extract texts from PDF. View preset
- Merge PDFs – Combine invoices, reports, attachments. View preset
- Extract Pages from PDF – Pull selected pages into new PDF. View preset
- Compress a PDF – Shrink file size by 70% easily. View preset
- Take a Website Screenshot – Capture websites into clear PNGs. View preset
Build your own custom API with our pdfUtils
Customize your PDF generation API Using JavaScript
Need full control over your PDF generator API? Our pdfUtils allows you to create customizable documents for HTML-to-PDF conversions, compress PDF files, merge PDF JavaScript, or extract pages. No servers. No advanced tools. Just your code, your rules.
const { PDF_MERGE, HTML2PDF } = require('./utils');
let pages = [
input.page1,
input.page2,
input.page3,
input.page4,
input.page5,
input.page6,
input.page7,
input.page8,
input.page9,
input.page10,
input.page11
];
pages = await Promise.all(pages.filter(i => i).map(i => HTML2PDF(i)));
return PDF_MERGE(pages);
This example shows how you can pass an array of HTML pages, generate a PDF for each one, and then merge them into a single file.
curl -X POST https://e.customjs.io/zeXXXy \
-H "Content-Type: application/json" \
-H "x-api-key: YOUR_API_KEY_HERE" \
-d '{
"page1": "<html>...</html>",
"page2": "<html>...</html>",
"page3": "<html>...</html>",
"page4": "<html>...</html>",
"page5": "<html>...</html>",
"page6": "<html>...</html>",
"page7": "<html>...</html>",
"page8": "<html>...</html>",
"page9": "<html>...</html>",
"page10": "<html>...</html>",
"page11": "<html>...</html>"
}' > test.pdf
This is how you would call your custom api.
Affordable HTML-to-PDF Conversion
CustomJS gives you 600 PDF/API calls every month for free, then scales from just $9 for 3,000+ calls, beating the "PDF-as-a-Service" incumbents on both cost and flexibility.
| Feature | CustomJS | ConvertAPI | DocRaptor | Api2PDF |
|---|---|---|---|---|
| Free Tier | 600 req/mo, no credit card | 250 trial conv. | None | None |
| Starter Plan | $9/mo | $30/mo | $15/mo | $1 base + usage |
| Billing Type | Per document (no setup) | Per conv. | Quota + usage | Time + file size |
| Integrations | Make.com, n8n, Zapier | REST API | PrinceXML | wkhtmltopdf, ChromeHead |
FAQs
What is a PDF API, and how does CustomJS help?
A PDF API lets you create, edit, and manage PDF files automatically with simple API calls. CustomJS offers a powerful API and an affordable option to build HTML-to-PDF workflows, merge PDF files, compress documents, and support a wide range of PDF actions, without expensive setup or server costs.
Can I use CustomJS to convert HTML to PDF?
Yes. Our HTML to PDF API makes it easy to convert dynamic HTML or CSS into pixel-perfect PDFs. You can build PDF creation flows within Make.com or n8n using our dynamic PDF generator.
How much does it cost to use CustomJS’s PDF API?
You can generate up to 600 PDF documents per month for free. After that, our starter plan is only $9 per month.
Can I merge multiple PDF files using CustomJS?
Yes, you can use our merge PDF API to combine invoices, reports, or multiple PDF documents into a single file quickly.
Does CustomJS allow me to compress PDF files?
Absolutely. Our compress PDF JS functionality lets you shrink PDF file size by up to 70% without losing quality.
Can I extract pages from a PDF with JavaScript using CustomJS?
Yes, you can use JavaScript to extract pages and create new files without extra tools.
Can I convert PDFs to images using CustomJS?
Yes. With CustomJS, you can easily convert PDF to PNG in your workflows.
Is CustomJS easy to integrate with Make.com and n8n?
Yes, you don't need any new server setup—just call our REST API.
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