IronPDF - SDK for creating and editing PDFs.
iTextPDF - iText offers flexible tools for PDF creation, editing and inspection.
PdfPig - Read and extract text and other content from PDFs in C# (port of PDFBox)
PDFSharp - Office & Productivity and Development
PDFJet - PDFJet is a mobile and cloud PDF Library for Java and .NET to generate PDF documents.
JSignPdf - JSignPdf is a Java application which adds digital signatures to PDF documents.