Annotation and Highlighting Tools for Document Enrichment

[Juan-glitch]

What feature would you like to see?

I am requesting a feature that enables users to annotate, highlight, underline, and add comments directly on documents, similar to what PDF readers allow. This functionality would make it possible to enrich documents with personal notes, clarifications, and highlighted sections without needing external tools.
Objectives:

Allow highlighting and underlining of text.
Enable insertion of comments, sticky notes, or side notes.
Provide simple drawing tools (arrows, boxes, shapes) to visually emphasize key areas.
Ensure annotations are saved within the document and remain editable.

Use Cases:

Reviewing technical or business documentation with contextual notes.
Marking key information or pending tasks.
Adding ideas or insights while reading.
Facilitating collaborative reviews and feedback.

Why is this needed?

Increased productivity by eliminating the need to export documents to PDF just to annotate them.
Centralized review workflow: annotations stay within the original file.
Smoother collaboration among team members.
Better knowledge retention and document clarity thanks to in‑context notes.

Additional context

No response

Before submitting

• I have searched existing feature requests to avoid duplicates

[github-actions]

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[dangtungg]

Hi @Juan-glitch, thanks for the detailed write-up on this.

A bit of context on how MarkView works, since it shapes what's feasible here: MarkView is a viewer, not an editor. It never modifies your source files. With that in mind, here's what we're exploring:

• Text highlighting with preset colors - select text, pick a color
• Inline comments attached to highlights for context or reminders
• Persistent storage - annotations saved per document URL in local storage, surviving page reloads
• Annotation sidebar - lists all highlights and notes with jump-to navigation
• Export support - annotations included when exporting to HTML

No timeline to commit to yet, but I'll update this issue as things move forward. One thing worth noting: since annotations live in local storage, they won't transfer if you switch browsers or clear your data. I'm considering an export/import as JSON option for backup purposes.

Outside our scope

A few items would take us beyond what a viewer extension can offer:

• Drawing tools - requires a canvas/SVG overlay approach that doesn't fit MarkView's current architecture
• Saving back to the file - MarkView has read-only access to your markdown files by design
• Collaborative reviews - this needs backend infrastructure (accounts, sync service), which is a different product category entirely

Thanks again for taking the time to write this up!

[Juan-glitch]

Hi @dangtungg,

Thanks for the detailed explanation — it clarifies the scope very well.

• Honestly, the experience you’ve built with Markdown and Mermaid is so smooth that it almost feels like working inside an IDE, which is probably why I momentarily overlooked the viewer-only boundary.

• The extension stands out — both in usability and overall polish — and it’s currently the best option I’ve come across.

Looking forward to seeing how the annotation features evolve!