Montecristo

PDF reader · Linux & Windows

PDF, finally in three dimensions.

Montecristo opens your documents instantly, lets you annotate, fill in and protect them — and when there's a 3D model inside, it spins right in front of you. Native, light, no telemetry.

U3D and PRC 3D models embedded in PDFs — finally on Linux too

Download free See what it can do
6
formats: PDF, EPUB, XPS, CBZ, FB2, SVG
14
standard annotation types
0
telemetry, accounts, ads
2
platforms, one native app on both

Why Montecristo

Five things that make the difference between a viewer and a working tool.

3D inside PDFs The headline feature

That 3D model was always there. Now you can see it.

Technical datasheets, CAD drawings, scientific papers: many PDFs contain 3D models that most readers show as an empty rectangle. Montecristo decodes them — both U3D and PRC — and puts them in your hands.

  • Rotate, pan, zoom with the mouse, smoothly.
  • Preset views X, Y, Z and isometric, with 60 fps animated transitions.
  • Four render modes: solid, wireframe, vertices, transparent.
  • Original colors, materials and textures from the model.
  • Broken-file safe: 3D runs in an isolated process; a corrupted model can't take the reader down with it.
Annotations

Write on the PDF like paper. Readable everywhere.

Highlight, underline, strike through, comment, draw. Every mark is saved as a standard PDF annotation: whoever receives the file sees it in Acrobat, Foxit, or any other reader.

  • Highlight, underline, strikeout and squiggly, anchored to the text.
  • Pen, sticky notes, free text, rectangles, ellipses, arrows, polygons.
  • Move, resize, rotate, copy and paste what you've drawn.
  • Quick palette and a free color picker.
  • Non-destructive saving: the original file is never rewritten in place.
Forms

Forms you can fill in. That do the math themselves.

Text fields, checkboxes, radio buttons, dropdowns, list boxes: all fillable right on the page. If the form has calculations or validation logic, Montecristo runs it.

  • Form JavaScript: totals, validation and calculated formats, run automatically.
  • Tab and Shift+Tab navigation, keyboard activation.
  • Required fields flagged, read-only fields respected.
Security

A PDF doesn't get to decide for you.

A document can contain links to other files, scripts and commands. Montecristo treats them for what they are: untrusted content. You decide what's allowed to happen.

  • No program is ever launched from a link in the document.
  • Separate permissions for internal jumps, other documents, the web, and new windows.
  • Form JavaScript can be switched off with one click.
  • Password-protect a PDF, with strength measured in bits as you type it.
  • Zero outbound connections: there is no networking code in the app at all.
  • Digital signatures for documents: coming soon.
Performance

A thousand pages, zero waiting.

Montecristo only renders what you're actually looking at, and prepares the next pages ahead of time. Scrolling stays smooth even on the heaviest documents, and the interface never freezes while it works.

  • Rendering on a separate thread, the next 6 pages pre-loaded.
  • Memory freed for pages that scroll out of view.
  • Performance panel: memory and cached pages, per tab.
  • MuPDF engine: compact, fast, battle-tested for years.

The philosophy

Three principles, in this order. If a new feature breaks one of them, it doesn't ship.

01

Actually light

Opens instantly and stays nimble even with documents thousands of pages long. No browser wearing an app costume: underneath is MuPDF, a rendering engine built to do exactly this, and do it well.

02

Native, not a compromise

A real GTK4 interface on Linux, the same care on Windows, with a native title bar and system snap. No Electron, no wrapper: it behaves the way your operating system taught you to expect.

03

Respects the reader

Zero telemetry, zero accounts, zero ads, zero connections. What you read stays on your computer. Full stop.

And then, everything else you'd expect

The basics of a good reader, built with the same care.

Multiple tabs

Many documents, one window. Drag files in: each opens its own tab, and a file that's already open won't be duplicated.

Not just PDF

Also reads EPUB, XPS and OpenXPS, CBZ comics, FictionBook and SVG, in the same interface.

Search and selection

Ctrl+F finds it instantly. Select text with the mouse and copy it wherever you need.

Outline and links

Clickable side outline, internal and external links, jumps between linked documents.

Images, one click away

Right-click an image on the page: copy it, save it, or read its EXIF data.

Watermark

Add a text watermark with the size, color, opacity and rotation of your choice.

Source view

For those who want to look under the hood: the PDF as indented text, editable object by object.

Zoom and rotation

Fit width or page, Ctrl+wheel zoom, instant rotation, middle-button pan.

Digital signatures Coming soon

Verify signatures on documents you receive, and sign your own PDFs with a certificate. Among the next things on the list.

English and Italian

Translated interface, with more languages on the way.

Download

Two platforms, three packages. Pick the one for your system.

Features: Full Minimal
Hardening: Standard Hardened

Two independent axes. The packages below are Full / Standard: every feature, built without the ENABLE_HARDENING flag. The Minimal variant (no 3D module, a niche feature that's also the heaviest to build) and the Hardened variant (extra symbol stripping/obfuscation — this build isn't insecure, that variant just doesn't exist yet) are planned but not published yet, and will be combinable with each other.

Linux

.deb package

For Ubuntu and Debian-based distros. Install with a double-click or apt.

Download .deb v0.1.19 · full build
SHA256
19cf0a71c5f1df89d1fafe3951a76cfe0343a3a78704daba67c29871ab0c273c
MD5
46e6459775cde1aa2e5f4b00807d230b
Linux

Portable build

Self-contained archive, no installation: extract and run.

Download .tar.gz v0.1.19 · full build
SHA256
80573f30eb44a868f2b9d14353c220b36ab4f35d5b2b7fc4495734137832b8a9
MD5
bcd98472413a4d7e7924adec816b9b1f
Windows

Windows executable

Windows 10 and 11, 64-bit. No separate dependencies to install.

Download .exe Not uploaded yet

Changelog

History of published versions. Full detail in the repository.

Version Date Highlights
0.1.19 2026-09-30 Rebrand to Montecristo (app ID, icons, .desktop entry). Fixed a packaging bug where the runtime anti-debug check (ptrace-based, Linux only) exited immediately on systems where ptrace is restricted for reasons unrelated to an actual debugger — the app simply wouldn't start after install, with no visible error. That check has been disabled on Linux; the rest of the hardening build is unaffected.
0.1.18 2026-09-28 First packaged build (.deb/.tar.gz) and site published. Italian/English localization. Fixed 3D model (U3D) colors and transparency. Fixed a page not rendering after a scrollbar drag; reopening an already-open file now focuses the existing tab instead of duplicating it. Password strength shown in bits, saving with imported annotations, viewer notes saved as standard PDF comments.
0.1.14 — "Fit width" zoom centers the page horizontally. Hand-drawn icons wired into the build.
0.1.13 — First version with an explicit SemVer number.
earlier — 157 commits with no explicit versioning: a GTK4 + native MuPDF viewer for Linux built from scratch — text search/selection, clickable links, U3D/PRC 3D annotations, password-protected PDFs, settings, document properties.