Work with Annotations in PDF via .NET SDK

API for manage annotations in PDF documents with .NET.

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Aspose.PDF Cloud SDK for .NET

Overview

    GitHub Learn Buy

    Most popular actions with Annotations in .NET

    Add new Annotations

    Get Annotations from PDF

    Replace Annotations in PDF

    Delete Annotations in PDF

    How to work with annotations in PDF documents using Cloud .NET SDK

    In order to work with annotations in PDF documents via Cloud .NET SDK , we’ll use Aspose.PDF Cloud .NET SDK This Cloud SDK allows you to easily build cloud-based PDF creator, editor & converter apps in C#, ASP.NET, or other .NET languages for various cloud platforms. Open NuGet package manager, search for Aspose.PDF Cloud and install. You may also use the following command from the Package Manager Console: PM> Install-Package Aspose.Pdf-Cloud

    Steps to add annotations using .NET SDK

    Aspose.PDF Cloud developers can easily load & append annotations to PDF documents in just a few lines of code.

    1. Uploads the PDF.
    2. Creates a styled text box (with fonts, colors, alignment).
    3. Submits the annotation to the specified page.
    4. Downloads the modified document for local use.
     

    This sample code shows adding annotations to PDF document

    
    public static async Task AddFreeTextAnnotation()
    {
        const string localPdfDocument = @"C:\Samples\sample.pdf";
        const string storageFileName = "sample.pdf";
        const string localFolder = @"C:\\Samples";
        const string resultFileName = "output_add_text_annotation.pdf";
        const int pageNumber = 1;

        // Get your AppSid and AppSecret from https://dashboard.aspose.cloud (free registration required).            
        var pdfApi = new PdfApi(AppSecret, AppSid);

        var filesOnStorage = await pdfApi.GetFilesListAsync("");
        if (filesOnStorage.Value.All(f => f.Name != storageFileName))
        {
            using var file = File.OpenRead(localPdfDocument);
            var uploadResult = await pdfApi.UploadFileAsync(storageFileName, file);
            Console.WriteLine(uploadResult.Uploaded[0]);
        }

        List<FreeTextAnnotation> annotations = new List<FreeTextAnnotation>
        {
            new FreeTextAnnotation(
                Name: "Freetext_NEW_Annotation",
                Rect: new Rectangle(100,350, 450,400),
                Flags: new List<AnnotationFlags>() { AnnotationFlags.Default },
                HorizontalAlignment: HorizontalAlignment.Left,
                Intent: FreeTextIntent.FreeTextTypeWriter,
                Justification: Justification.Center,
                RichText:                       "NEW FREE TEXT ANNOTATION 2",
                Subject:                        "Free Text Box Subject 2",
                Contents:                       "Free text annotation sample contents 2",
                Title:                          "This is a free text annotation 2",
                ZIndex: 1,
                TextStyle: new TextStyle(
                    FontSize:        20,
                    Font: "Arial",
                    ForegroundColor: new Color( A: 0xFF, R: 0x00, G: 0xFF, B: 0x00),
                    BackgroundColor: new Color( A: 0xFF, R: 0xFF, G: 0x00, B: 0x00)
                ),
                Modified: "03/27/2025 00:00:00.000 AM"
            )
        };
        AsposeResponse response = await pdfApi.PostPageFreeTextAnnotationsAsync(storageFileName, pageNumber, annotations);

        if (response == null)
            Console.WriteLine("NewFreetextAnnotation(): Unexpected error!");
        else if (response.Code < 200 || response.Code > 299)
            Console.WriteLine("NewFreetextAnnotation(): Failed to append text annotation to the document.");
        else
        {
            await (await pdfApi.DownloadFileAsync(storageFileName))
                .CopyToAsync(File.Create(Path.Combine(localFolder, resultFileName)));
            Console.WriteLine("NewFreetextAnnotation(): annotation added to the document '{0}.", resultFileName);
        }
    }