The right PDF API is one that handles your biggest real document within your plan, not one that renders a neat one-page sample. Pick an approach first: an HTML-to-PDF engine, a template designer or a wider PDF toolkit. Then read how each plan counts usage, because credits, documents and file size are measured differently from one vendor to the next.
A one-page sample is the easiest PDF you'll ever generate, and it's the one most trials get judged on. Your real invoices, reports and contracts are longer and heavier, full of images, tables and fonts. Below are nine APIs, in no particular order, grouped by how they make the PDF: engines that convert HTML, designers that fill templates, and toolkits that do more than create.
How usage gets counted
Credits don't mean the same thing from one vendor to the next. PDFShift's plan page says a 14 MB document counts as 3 credits, so the size of each file changes how much of your allowance it uses. DocRaptor's plan page describes a free plan with no overage allowed, so once you reach the limit, generation stops rather than carrying on. Others count documents, whatever their size.
None of this is a trick. A heavy, image-rich report and a one-page receipt can simply use your allowance at very different rates, and a free plan that looks generous in a demo may behave differently with your own files. Before you compare plans, get answers to these:
- Is usage counted per document, per page, per credit or by file size?
- What happens at the limit: does generation stop, or does it carry on and bill the extra?
- Do failed or retried conversions count?
- Are test documents counted the same way as live ones?
Engines, templates and toolkits side by side
| Tool | Approach | Good for |
|---|---|---|
| Anvil | Document workflow API | Filling and e-signing PDFs by API |
| Api2Pdf | Serverless PDF toolkit | HTML, URLs, Markdown and Office files to PDF |
| APITemplate.io | Template designer | PDFs and images from the same templates |
| CraftMyPDF | Template designer with no-code connectors | Templates run from Zapier, Make, n8n or Bubble |
| DocRaptor | HTML to PDF engine | Print-style HTML with CSS Paged Media |
| PDF Generator API | Template designer | A template editor aimed at developers |
| PDF.co | PDF toolkit | Extracting, editing, merging and splitting PDFs |
| PDFMonkey | Template-based generation | Dynamic templates managed in a dashboard |
| PDFShift | HTML to PDF engine | Converting HTML, CSS and web pages to PDF |
HTML-to-PDF engines
An engine takes HTML and CSS you already have and prints it as a PDF. If your invoices or reports already exist as web pages, this is the shortest route: developers style them with the CSS they know, and the engine does the rest. The two engines here are the ones from the counting section: one built on PrinceXML with CSS Paged Media support and compliance claims, the other a conversion API for HTML, CSS and live web pages.
CSS Paged Media matters if you need page numbers, running headers and footers, or control over where pages break. Ask each engine how it handles long tables that cross pages, web fonts and images that load late, because those are common trouble spots in generated documents.
Template designers
Template designers turn the work around. You design the layout once, often in a visual editor, then send data to the API and get a finished document back. That helps when someone other than a developer owns the look of the invoice. PDFMonkey keeps dynamic templates in a dashboard and generates through a REST API. APITemplate.io produces PDFs and images from the same reusable templates, handy if the same data also needs to become an image. PDF Generator API offers a template editor aimed at developers.
The question to ask here is how a template copes with variable length: an invoice with three lines and one with three hundred. Build your longest real example before you commit.
PDF toolkits and document workflows
Some jobs go beyond creating a fresh PDF. Api2Pdf generates PDFs from HTML, URLs, Markdown and Office files, and merges, watermarks and adds barcodes, through one serverless REST API. PDF.co extracts, edits, converts, merges and splits documents, which helps when your workflow receives PDFs as well as sends them. Anvil is document infrastructure for AI agents: it collects data, fills PDFs and gets them signed over an API.
If your contracts need signing, or your process starts with a PDF someone else sent you, look in this group before you look at a pure generator.
If you build without code
Not everyone generating PDFs writes code. CraftMyPDF connects to Zapier, Make, n8n and Bubble as well as offering a REST API, so a form submission or a new row in a sheet can produce a finished document without a developer. Design the template once, map the fields in your automation tool, and test with a full record, including the longest values your customers type in.
All nine APIs, A to Z
Anvil
Best for: Products where AI agents or apps collect data, fill PDFs and get them signed over an API, rather than only generating new documents.
Api2Pdf
Best for: Developers who want one pay-as-you-go serverless REST API that turns HTML, URLs, Markdown and Office files into PDFs, merges and watermarks them and makes barcodes.
APITemplate.io
Best for: Teams generating both PDFs and images from the same reusable templates through one API.
CraftMyPDF
Best for: No-code builders who design a PDF template once, then generate documents and images at scale through Zapier, Make, n8n, Bubble or a REST API.
DocRaptor
Best for: Developers converting HTML to PDF with PrinceXML and CSS Paged Media, from a vendor that claims SOC2 and HIPAA compliance and guaranteed uptime.
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PDF Generator API
Best for: Engineering teams who want PDF documents created automatically from templates built in an editor aimed at developers.
PDF.co
Best for: Workflows that need to extract, edit, convert, merge and split existing PDFs as well as create them, with 3,000+ integrations by the vendor's claim.
PDFMonkey
Best for: Builders who want to create, manage and automate PDF generation from dynamic templates kept in a dashboard and called through a REST API.
PDFShift
Best for: Anyone converting HTML and CSS documents or live web pages to PDF, with the vendor claiming high-fidelity conversion and no maintenance on your side.
My advice on picking a PDF API
Choose by who'll own the layout. If developers already have the document as HTML, an engine is the simplest route and keeps everything in code. If a designer or operations lead needs to change the invoice without waiting for a release, a template designer saves a queue of small requests. If PDFs arrive as well as leave, or need signatures, go to a toolkit or workflow API.
Then judge every name on your shortlist by your heaviest file, not the vendor's demo. If you're converting or editing files by hand rather than by API, my guides to PDF converters and document automation software cover that side.
Your largest real document: a test checklist
- Pick your heaviest real document: the longest report, the invoice with the most lines, the contract with the most images.
- Generate it on every trial and note its file size and how the plan counts it.
- Check page breaks, headers, footers, fonts and any table that crosses a page.
- Generate it several times in a row and see what happens as you near the plan limit.
- Send one broken request on purpose, such as a missing image, and see whether it's counted.
- Ask how long generated files are stored and how you delete them.
If an API passes on your worst document, the easy ones will look after themselves.
Do you make PDF generation APIs? Tool makers can ask to be considered for a featured place on this list.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
What's the difference between an HTML-to-PDF API and a template API?
An HTML-to-PDF API converts HTML and CSS you've already built. A template API stores a layout you design once, then fills it with the data you send in each request.
Can I generate PDFs without writing code?
Yes. Some template tools connect to no-code automation platforms, so a form or spreadsheet row can trigger a finished document. You'll still need to design the template and map the fields.
Why does my PDF use more credits than expected?
Some plans count by file size or credits rather than documents, so a large, image-heavy file can use more of your allowance than a one-page sample. Check how each plan counts usage before you go live.
What's CSS Paged Media?
It's the part of CSS that controls printed pages: page size, margins, page numbers, running headers and footers, and where pages break.
Can a PDF API fill and sign existing forms?
Some can. Workflow APIs fill existing PDF forms and send them for e-signature, which goes beyond creating a new document. Check for this if contracts are part of the job.
