Show HN: Papermill Press – An AI-friendly markup language for PDF generation

Posted by davidpapermill 1 hour ago

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If you’ve generated PDFs from HTML, you’ll know the pain: headless Chrome in Docker, CSS hacks, content that flows over pages or table boundaries and other quality issues.

The fundamental problem is that HTML was designed for screens, not print.

We built Press, a markup-based document language where pages, content flows, and assets are first-class concepts. Content can flow across frames, columns, and pages without manual pagination. Pages are created dynamically based on the available content.

Press templates separate layout from content. You can send markdown, Press markup, or a mixture of both to the API. Data can be sent in JSON, CSV, XML.

Because Press is XML-based it can easily be generated by agents - some of our users are generating complete documents in a single shot, although the language is designed for repeatable automation.

You can also use our MCP server, which enables models to design templates.

A simple API call sends a markdown payload, which is injected into a <flows><body>…</body></flows> element in Press:

  curl -X POST https://api.papermill.io/v2/pdf?template_id=papermill-modern-report \
    -H "Authorization: Bearer $PAPERMILL_API_KEY" \
    -H "Content-Type: text/markdown" \
    --data-binary @- \
    -o report.pdf <<'EOF'
  # Q3 Revenue Summary
  
  Quarterly performance across our core product lines.
  
  | Product  | Revenue  | Growth |
  |----------|----------|--------|
  | Platform | £482,000 | +18%   |
  | Add-ons  | £124,000 | +42%   |
  | Services | £67,000  | -3%    |
  
  Strong quarter overall, driven by add-on adoption.
  EOF
PDF output: https://mill.pm/hn

Pages and frames in Press can declare dependencies on a content flow like the <body> above. By default, if there’s no content in the flow then the frame or page won’t be generated. You can run flows between frames and pages, and combine multiple flows on a page - for example, a sidebar can run across pages until no content is left, then make room for body content. This makes it possible to implement complex layouts.

You can mix markdown and Press:

  # Visualisation

  Sometimes it's *useful* to mix both markdown and Press:

  <visualization>...</visualization>
The typesetter adapts to dynamic content (e.g. LLM output). For example, tables and columns can be automatically sized and Papermill will even auto-rotate a table and its page to fit if needed.

Templates support components, repeating over data, document logic, and conditional styling. We mostly use an inline-styling approach, and provide the concept of a style “alias”, which is a bag of styling properties you can reuse and compose.

Here’s an example template written in Press, our document language. It uses the first page layout until the sidebar flow is exhausted, then switches to the second:

  <press>
    <document format="A4" page-margin="2cm">
      <repeat flow="sidebar">
        <page>
          <frame direction="row">
            <frame padding-left="1cm" padding-right="1cm"><flow name="body" /></frame>
            <frame width="20%" background-color="#f5f5f5" padding="0.5cm" font-size="9pt"><flow name="sidebar" /></frame>
          </frame>
        </page>
      </repeat>
      <repeat flow="body">
        <page><flow name="body" width="fill" /></page>
      </repeat>
    </document>
    <flows>
      <body type="markdown"><lipsum paragraphs="10" /></body>
      <sidebar type="markdown"><lipsum paragraphs="3" /></sidebar>
    </flows>
  </press>
Papermill is a paid API with a free tier. Press is the document language.

Try it for free: https://app.papermill.io/signup (no credit card needed)

Docs including MCP setup: https://docs.papermill.io

Data-only sandbox: https://app.papermill.io/demo.html (no email needed)

We're a small team based in Manchester, UK. Tom (CTO) and I are happy to answer questions about the language design, the rendering engine, or anything else!

Comments

Comment by davidpapermill 1 hour ago

Hi Folks - I'm David, CEO of Papermill. We're super excited to get feedback on what we're building. This is the first time we've posted to a forum. Designing a document language for AI is a major undertaking and we'd love to hear from folks with experience and interest in document languages and generation.

Comment by tomfitzsimmons 46 minutes ago

I'd love to see something like this in chatgpt or claude. The PDFs you can generate there are always so boring.

Comment by davidpapermill 42 minutes ago

Thanks Tom, good to see you on HN! You can connect Papermill to your favourite agent via MCP - we prefer Claude Code.

https://docs.papermill.io/mcp/#using-the-papermill-mcp-serve...

You can ask Claude to generate templates, full documents, ask it about the Press language, save templates, ask it about templates and more. There's a lot more to it - design guidelines for print vs web, recipes in Press etc.

I've tried it with Fable already and it's a noticeable improvement - we support visual feedback through MCP and I think that's helping Fable a lot.

Comment by tompapermill 39 minutes ago

Hi Tom,

One of the things we've learned is that models often need more guidance when generating documents. We give real-time feedback to models as they're constructing the document, such as "you have content here that you've done nothing with and doesn't appear in the report as it likely overflowed off the page, you should think of a way to handle this" and "this image is sized incorrectly and just will not fit in the area you've specified".

Giving models the tools to create media for print allows both the user and the model to experiment with more wild designs, knowing that things will not randomly break!

Comment by frantzalot 44 minutes ago

As a solicitor myself managing a high street law firm that is already comfortable drafting, reviewing, and producing client-ready PDFs from Word, where is the return on investment in adopting Press? What can Press do that cannot be achieved with Word and existing document automation tools?”

Comment by davidpapermill 40 minutes ago

Papermill is more the "infrastructure" layer that sits below legal AI tools - we don't work directly with law firms, rather more likely to be used by a startup building a legal tool. Companies like Wordsmith, Legatics, Legora, Harvey can use Papermill to output high-quality PDFs.

That said, an export from Word to Papermill templates might be a nice addition...

Comment by off_by_two 22 minutes ago

Looks interesting. Are there any limits on the file size or length of pages that can be produced?

Comment by tompapermill 17 minutes ago

Hi off_by_two

We don't apply hard limits on PDFs. We've handled PDFs of over 1GB and close to 1000 pages.

We also have a large document service that handles extremely large PDFs in the background.

Comment by davidpapermill 7 minutes ago

Worth adding that we also support the integration of many PDFs into a large document, including complex processing, but this is not part of the publicly accessible Press language (yet).

Comment by tompapermill 1 hour ago

Hi, Tom here. I'm happy to answer any questions r.e., generating PDFs, better ways of making automated document workflows more robust, or anything related to Papermill and Press!

Comment by Ste_CreaTech 1 hour ago

I'm excited to see more about how Papermill and Press can interact with agents in agentic workflows! This seems like a great problem solved in AI-first startups.

Comment by davidpapermill 48 minutes ago

Press is designed from the ground-up for agentic workflows. We spoke to hundreds of companies generating PDFs before we designed the language, and had been building AI design systems ourselves for a few years.

You can connect an agent to our MCP server, see: https://docs.papermill.io/mcp/#using-the-papermill-mcp-serve...

It's quite amazing to see what Claude can do when it has a tool like Papermill at its disposal - worth connecting and having a play.

In practice, you can either directly connect an LLM to the MCP server, or send via the API after (say) cleaning up LLM output, combining it with RAG and other data etc.

Comment by tompapermill 1 hour ago

Thanks Ste, we're happy to answer any questions you've got!

Comment by lmartinneuwave 30 minutes ago

looks great dave! loved the product. Hope it all goes well.

Comment by tim_at_ping 1 hour ago

V cool. Glad to see another Manchester based start up!

Comment by Ste_CreaTech 1 hour ago

Byteful seems cool! WEb proxy stuff is important for me in my near future so I may just check you out. Thanks for commenting!

Comment by davidpapermill 1 hour ago

Thanks Tim! Great to see Byteful doing so well too!