If your application has to show users a document, you have two ways to do it: send them the file and hope they own the right software, or render it yourself. This post is about the second.
Doconut Viewer is the .NET document viewing SDK. It installs into your application and renders documents server-side, so nothing is downloaded to the user's machine and nothing is installed on it. Note the product name: Doconut.app is the free website where you can try the same engine on one file, and it is not the thing you install.
Multi-Format Support
The SDK catalogue is 75 file extensions across 18 families, so your application can open the formats that actually arrive in a business inbox: PDFs, Office documents, CAD drawings, Visio diagrams, Project plans, email files, eBooks and images. Recent additions include EMF, AVIF and the macro-enabled Office variants, so files that used to be refused now open.
DICOM is part of that 75, through a separately licensed plugin. The free viewers on Doconut.app accept 73 — everything except .dcm and .ima.
User-Friendly Interaction
Engagement is key to user satisfaction. Doconut.app offers intuitive controls that make document navigation simple and efficient. Users can zoom, navigate pages, and rotate documents effortlessly. The quick access to thumbnail views also allows for efficient document navigation, enabling users to locate the information they need in a matter of seconds.
Comprehensive Annotation Tools
Annotation is one of four plugins licensed on top of the viewer — the others are Converter, DICOM and Search. With it, users can leave text comments, highlight sections, add sticky notes, and use shapes and stamps.
It is worth being clear that this is a separate purchase rather than a feature of the base viewer, and worth deciding whether your workflow needs it before you budget for it. Plenty of applications only ever need to display a document.
Advanced Search Functionality
Doconut.app searches the text layer a PDF already carries, and shows each hit where it sits in the page layout rather than as a bare list of line numbers. That covers the documents most teams work with: anything exported from Word, produced by a reporting system, or scanned with text recognition switched on. A page held only as an image has no text to search, and reading characters off the image is not something the viewer does today.
Flexibility in Integration
The SDK supports ASP.NET, MVC, .NET Core, .NET 6+ and Blazor. Because it is installed in your own environment rather than called as a service, it deploys wherever your application already deploys, and it makes no calls to Doconut servers — which is usually the answer a security reviewer is looking for.
Performance and Scalability
Rendering happens on the server. That is what lets a browser display a DWG on a machine with no CAD software, and it is also the cost to plan for: the work moves to your tier. Test with your heaviest real documents rather than samples, and look at the resolution and caching settings before concluding you need more hardware.
Customization Opportunities
The viewer's appearance and its set of controls are configurable, so it can look like part of your product rather than a window into someone else's. Take the option names from the documentation for the version you installed; they have changed between releases.
The more useful decision is which controls each role should see. Whether a user can print or download is a permission question your application already knows the answer to.
Where to Start
The trial licence is free. Start from the download page, and use the live demos first if you want to see the rendering before you write any integration code.
Two things worth testing before you commit: your ugliest real document, and the formats you actually receive rather than the ones on the list. Sample files always pass.
And if you only needed to open one file today rather than build anything, Doconut.app will do that in a browser tab, free, and delete it afterwards.