Built around your privacy
>_
Read and edit PDFs, Markdown and images. Sign and bring PDFs together. A powerful workspace, right here on your Mac.
macOS 14 or later Apple Silicon v1.1 (41)
01 / Free · Open source · Private
PDF: Private Document Fortress costs nothing and reports nothing. The full source is open under the AGPL-3.0 license — no subscription, no accounts, no network services.
02 / Local AI by design
Custōs is a document assistant that answers from your file, on your Mac. It is local by design — the inference engine ships inside the app, so nothing about your document is ever shared with a third party.
03 / Double view
Open a second PDF beside the first and reference across both — a contract against its amendment, a translation against the original, figures against the appendix.
Aster & Co. × Northstar Studio
Client shall pay each undisputed invoice within thirty (30) days of receipt. Overdue balances accrue interest at 1.5% per month.
Fees are stated in USD and exclude applicable taxes. Approved expenses are invoiced monthly with supporting receipts.
Effective 17 October 2026
Section 4.2 is replaced as follows: “Client shall pay each undisputed invoice within fifteen (15) days of receipt. Overdue balances accrue interest at 1.0% per month.”
All other terms of the Agreement remain unchanged and in full force and effect.
04 / Clipboard tray
Drag a rectangle over any PDF page or image with Copy Area. Each clipping lands in a tray shared across every tab and window — and on your system clipboard, ready to paste into any app.
05 / Markdown
PDFs are great for reading what’s already there, but Markdown is where your own ideas come to life. Instead of making you switch between different apps, we built one seamless workspace where you can turn PDFs into editable text, take smart notes, and publish finished products.
# Weekly notes
**Friday, 17 October 2026**
## Launch checklist
- [x] Review the **Q3 report**
- [ ] Share the revised draft
> Drafts stay local.
> Nothing leaves this Mac.
### Next up
1. Proofread the introduction
2. Export the final PDF
`⌘S` saves with original line endings.
Ever stumble upon an amazing PDF and wish you could save it to your personal knowledge base? Now you can. Convert locked PDFs into clean, fully editable Markdown files with a single tap.
See your formatting happen instantly. With our side-by-side live preview, you can type in clean Markdown on the left and see exactly how it looks fully rendered on the right as you type.
Read and highlight your PDFs on one side, and jot down your thoughts in pure Markdown on the other. No messy font settings, no alignment headaches—just pure focus on your thoughts.
Bring your work across the finish line. Once you’re done writing in Markdown, turn your notes into a beautifully formatted PDF report with just one click, ready to send to your team or client.
Markdown is the go-to format for modern note-taking and AI tools. It’s lightweight, works everywhere, and keeps your digital brain clean, organized, and future-proof.
06 / The rest of the toolkit
A native Mac editor for every PDF job — built with SwiftUI, AppKit, PDFKit and the bundled PDFium engine.
Edit existing PDF text in place, add styled text boxes, highlight by text or area, draw freehand, and insert images — every change undoable, every annotation still vector after saving.
Timestamped threads with replies in a resizable sidebar. Anchor comments to any point or to selected text, then resolve, accept or reject — saved as standard PDF annotations other readers understand.
Lines, arrows, rectangles, ellipses, chat bubbles, ticks and crosses. Move, bend, rotate and restyle after placing — or draw your signature directly on the page.
A dedicated Redact tool for content that must not travel with the file — separate from annotations, so what you black out stays out.
Drag thumbnails to reorder, rotate or delete pages, merge PDFs with reordering before combining, extract a range, or split selected pages into separate files.
Conversion that respects the layout. Every enhanced export ends in a review: the original next to the generated Word preview, the differences marked, and whether AI was actually used — stated plainly.
Each source page, paper size, font styling and text-free artwork is retained — stored in editable Word text boxes. Ideal for dense reports and forms. No AI model required.
Real paragraphs, native lists and bordered tables that reflow as you edit — reconstructed on-device, with optional local AI and five candidate layouts compared side by side.
07 / FAQ
Clear answers about PDF: Private Document Fortress, its local privacy model, supported formats and macOS requirements.
Yes. PDF: Private Document Fortress is a free macOS workspace for PDF, Markdown and image files, licensed under AGPL-3.0. Every feature is unlocked, with no subscription, in-app purchases or trial period.
No. Reading, editing, annotation, conversion and export happen locally on your Mac, with no accounts, analytics or telemetry. The only network exception is an optional AI model download from Hugging Face, which happens only when you request it.
Custōs uses MLX models that you download or import, together with an inference engine bundled in the app. It requires no account or API key, and its answers can include page citations that open the matching PDF passage. Without a model, supported features use geometric methods and disclose the fallback.
PDF: Private Document Fortress opens PDF and Markdown files, plus PNG, JPEG, HEIC, TIFF, BMP, GIF and WebP images. These formats share one local workspace for reading, editing, annotation and export.
Yes. PDF-to-Word conversion and OCR run on-device. Match PDF layout preserves positioned content without AI; flowing paragraphs and tables can optionally use local AI. LibreOffice is used for enhanced previews when installed, and the app explains its fallback preview when LibreOffice is unavailable.
PDF: Private Document Fortress requires macOS 14 or later on Apple Silicon. The available local development build is not notarized, so macOS may ask you to confirm before opening it. You can also build from source without an Apple Developer account.
08 / Get the app
VERSION 1.1 (41)
Completely free and open source. This is a local development build and has not been notarized for distribution — macOS may ask you to confirm before opening it. Build it yourself from source:
$ zsh Scripts/build.sh
$ zsh Scripts/test.sh
Or open Private Document Fortress.xcodeproj in Xcode and press ⌘R. Ad-hoc signed — no Apple Developer account required.