Documentero - Turn your documents into templates that can generate .docx or .pdf documents using shareable forms or API
Apache PDFBox - The Apache PDFBox™ library is an open source Java tool for working with PDF documents.
Docmosis - Document generation software
iTextPDF - iText offers flexible tools for PDF creation, editing and inspection.
Sigstr - Email signature marketing
IronPDF - SDK for creating and editing PDFs.