📄 mdseal
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Seal your documents. Prove they have not changed.

mdseal turns your Markdown and HTML into PDF, slides or PowerPoint, then seals the PDF as PAdES and timestamps it with a third party. A sealed document cannot be altered without it showing.

Convert a document How it works

Integrity, proven

The slightest change invalidates the seal, and any reader says so. This is what mdseal genuinely guarantees.

Date attested by a third party

An independent timestamping authority attests to the moment of sealing. Without one, the date would be declared by the signer — and therefore backdatable.

Restrictions, and what they are worth

AES-256 encryption writes permissions into the file: no printing, no copying. Serious readers honour them, but the PDF format lets nobody enforce them. What is enforceable is the seal.

Converting needs no account. Sealing does — creating one is free and immediate.

Convert Markdown / HTML → PDF · PPTX

Built from the @mostajs/doc-* stack: Markdown editor with live preview, contrast-checked themes, Chrome and pandoc engines.

Aperçu…

Toolbar, live preview and file import. In HTML mode the preview is indicative only; the conversion itself honours the HTML you supply.

File (optional) A file replaces the text above; its type is inferred from the extension.
Input
Output PPTX expects Markdown: level-2 headings open the slides.
Signature (optional)

Engine : PAdES + permissions (pyhanko) — Signature avancée et permissions restrictives disponibles.

With no certificate uploaded, mdseal signs with the server’s own. The key and its passphrase live in memory only, for the duration of the signature, and are never written to any log.

Document protection

Once set, it becomes the only hard lock — but it locks OPENING, not use: the document no longer opens without it, in any reader, and whoever has it can then print and copy. Left empty, the document opens freely.

⚠ mdseal does not keep this password: lose it and the document is lost with it.

What the document allows

A ticked box means ALLOWED. That is what the PDF format means, and what any verifier will display: unticking “Printing” reads as print_highres: False.

Allowing high-resolution printing also allows plain printing: the format ignores the “high quality” bit when printing is refused.

Filling form fields stays allowed and is not in this list: sealing requires it, because a signature field is a form field. A PDF that already had fillable fields keeps them.

⚠ These restrictions are INSTRUCTIONS, never locks — with a password as without. Serious readers honour them; a tool that chooses to ignore them can, and the PDF format offers no way to stop it. The password protects access, never use: whoever has it can save a copy unencrypted and fully allowed. What is genuinely enforceable is the signature — see the help.