Step 1: Download the latest version of Spire.PDF Pack from the link below, unzip it, and you'll get the DLL files for .NET Standarad from the "netstandard2.0" folder. If you already have this folder in your disk, go straight to step two.

Step 2: Create a .NET Standard library project in your Visual Studio.

Step 3: Add all DLL files under the "netstandard2.0" folder as dependencies in your project.

Right-click "Dependencies" – select "Add Reference" – click "Browse" – selcet all DLLs under "netstandard2.0" folder – click "Add".

Step 4: Install the other five packages in your project via the NuGet Package Manager. They are SkiaSharp, System.Buffers, System.Memory, System.Text.Encoding.CodePages and System.Runtime.CompilerServices.Unsafe.

Right-click "Dependencies" – select "Manage NuGet Packages" – click "Browse" –type the package name – select the package from the search results – click "Install".

Step 5: Now that you've added all the dependences successfully, you can start to write your own .NET Standard library that is capable of creating and processing PDF documents.

using Spire.Pdf;
using Spire.Pdf.Graphics;
using System.Drawing;

namespace SpirePdfStandard
{
    public class Class1
    {
        public void CreatePdf()
        {
            //Create a PdfDocument object
            PdfDocument doc = new PdfDocument();

            //Add a page
            PdfPageBase page = doc.Pages.Add();

            //Draw text on the page at the specified position
            page.Canvas.DrawString("Hello World",
                                    new PdfFont(PdfFontFamily.Helvetica, 13f),
                                    new PdfSolidBrush(Color.Black),
                                    new PointF(50, 50));

            //Save the document
            doc.SaveToFile("Output.pdf");
        }

    }
}