Watermark annotations are visible text or image marks over an Excel spreadsheet to show ownership or identify confidential information. These can be useful for spreadsheets that are shared for review, circulated internally, or sent to customers and business partners. Labels such as “Confidential,” “Draft,” or “For Review” can give recipients useful context as soon as they open the file, without changing the underlying spreadsheet data. In this guide, you’ll learn how to add watermark annotations to XLS files in C# using the .NET REST API. You can customize the annotations to suit the spreadsheet, including its position, appearance, and visibility. This makes it easier to mark different types of Excel files according to how they are used.

Steps to Add Watermark Annotations to XLS in C# .NET

1. Install GroupDocs.Annotation Cloud SDK for .NET from NuGet
2. Set up your client credentials with the Configuration class
3. Initialize the AnnotateApi class and add the source XLS file
4. Create a watermark annotation and define its properties with AnnotationInfo
5. Apply the annotation options with AnnotateOptions
6. Add a watermark annotation to the XLS file using the Annotate method

The step-by-step process starts by adding an XLS file you want to mark and deciding where the watermark should appear. Then, create the watermark annotation and provide its text. You can customize properties such as font, size, opacity, position, and color. When the annotation is ready, send the request through the .NET REST API and save the resulting XLS file. The spreadsheet data and structure remain available while the watermark adds a visual layer. Adding watermark annotations to XLS files can make spreadsheet handling more practical. They give viewers immediate context without requiring a separate note or message about the file’s status. For organizations managing many Excel files, a watermark can become part of an existing document workflow. Because the appearance can be adjusted, you can choose settings that remain visible across multiple XLS documents.

Code to Add Watermark Annotations to XLS in C# .NET

Watermarks are a simple method to add context, ownership information, or confidentiality notices to XLS files. With the GroupDocs.Annotation Cloud .NET SDK, you can add watermark annotations to XLS in C# and adjust their placement and appearance for different spreadsheet needs. The .NET REST API enables marking of XLS workbooks consistently across individual documents or larger document-handling workflows. If you are preparing a spreadsheet for internal review, a watermark annotation provides an additional visual indicator without obstructing the existing document information. As a developer, our Cloud API lets you distinguish working copies from finalized files and makes the status of a spreadsheet more obvious to anyone viewing it.

Looking to annotate other document formats? If so, check out the related article on adding strikeout annotations to PDFs with the .NET REST API.