Comment on a PDF, and search the text it already carries—without plug-ins.
Introduction
Many organizations use PDFs as their primary document format for reports, research papers, manuals, and technical drawings. In many .NET applications, users can upload a file and open it in a viewer—but that’s where the workflow stops.
A traditional viewer provides only a read-only experience, leaving users unable to mark up a document or find a phrase without scrolling for it.
By adding annotation and text search to a modern plug-in-free PDF viewer, .NET applications let people comment on a file and jump straight to the passage they need — provided the PDF carries a text layer, which most do.
In this article we’ll explore:
- How PDF annotation improves document review workflows
- How full-text search reads the text layer of a PDF, and which files it cannot help
- How easily these features can be integrated into a .NET application
You can try the viewer or download the SDK from:
1. PDF Annotation – Turning Static Pages into Interactive Documents
The problem with static PDFs
Many teams still rely on inefficient workflows when reviewing documents:
- Print the PDF
- Mark it with a pen
- Scan the document
- Upload a new version
This process creates version confusion, delays, and unnecessary manual work.
The solution: an annotation layer in the viewer
Embedding an annotation engine into your .NET portal lets users interact with the document in place.
One licensing note before the feature table, because it affects the budget rather than the design: annotation is a separate plugin for Doconut Viewer, not part of the base viewer. It is one of four — Annotation, Converter, DICOM and Search. Text-layer search, discussed in the next section, is likewise the Search plugin. Controlled printing, by contrast, is part of the viewer itself.
| Feature | Benefit |
|---|---|
| Highlight, underline, strikethrough | Quickly emphasize important text |
| Sticky notes | Add contextual feedback directly inside the document |
| Freehand drawing | Useful for diagrams, technical sketches, and design reviews |
| Timestamped annotations | Track when changes were added |
Instead of modifying the original file, annotations can be stored as separate metadata layers (for example JSON) linked to the document.
This approach ensures:
- The original PDF remains unchanged
- Annotations can be exported or removed independently
- The document remains the single source of truth
Practical impact
Annotation dramatically improves document workflows:
- Faster document reviews
- Clearer feedback during design or research discussions
- Reduced need for external editing tools
2. Full-Text Search – What a PDF Has to Carry
Two PDFs that look identical
Open two scanned contracts side by side and they can look the same. One is searchable and the other is not, and nothing on screen tells you which is which.
A PDF stores page images and, separately, a text layer: the characters of the page and the position of each one. Almost every PDF that came out of Word, a report generator, an export from a business system, or a scanner with text recognition switched on carries that layer. Search matches your phrase against it and highlights the spot on the page image where those characters sit.
A PDF that is only a photograph of a page carries no such layer. There is no text in the file, so there is nothing for search to match.
What the viewer does with the text layer
| Capability | Description |
|---|---|
| Text-layer search | Matches the query against the characters stored in the file |
| Hit highlighting | Marks each match in place on the rendered page |
| Result navigation | Steps from one hit to the next across the whole document |
| Any script | Reads the layer as written, Latin or not |
Where the layer is present:
- text is selectable
- users can copy content
- full-text search works across the whole file
Where it is absent, the file still opens and renders normally; it simply cannot be searched. Doconut does not currently read characters out of a page image.
Why this matters
Whether a document is searchable is decided when it enters your system, not when somebody needs to find it. Scanners and document management platforms can nearly all write a text layer on ingest, and a file that arrives with one stays useful for as long as you keep it.
Across an archive captured that way, users can instantly find:
- technical specifications
- regulatory clauses
- scientific references
- historical records
Instead of manually reviewing documents, they can simply search and jump to the relevant section.
3. Simple Integration in .NET Applications
Take the package name, the version and the initialization steps from the official download page and the documentation shipped with the build you install. Both have changed across releases, and a package line copied from an article is the most common reason a first integration fails in a way that looks like a licensing error.
The viewer works with common .NET frameworks including:
- ASP.NET Core
- ASP.NET MVC
- Blazor
Once configured, your application displays PDFs directly in the browser. Annotation and text search appear once their plugins are licensed and enabled.
4. Plug-In-Free and Secure by Design
Modern browsers no longer support legacy plug-ins like Flash or ActiveX.
A modern PDF viewer must run entirely in HTML5 and JavaScript.
Key benefits include:
- No client-side installation required
- Works across modern browsers
- Compatible with desktop and mobile devices
Security features typically include:
- HTTPS-only communication
- token-based authentication
- controlled document access
This makes the viewer suitable for enterprise applications handling sensitive documents.
Conclusion
Static PDFs limit how teams work with information. Adding annotation and text search to your .NET application turns a file people could only read into one they can comment on and search through.
Key benefits include:
- Faster document review through annotation tools
- Full-text search wherever the PDF carries a text layer, which is most of them
- Easy integration into existing .NET applications
- Plug-in-free viewing experience
If you want to explore these capabilities further, you can learn more or download the product from:
Give your readers a PDF they can mark up and search, inside the application they already use.