Apache PDFBox - The Apache PDFBox™ library is an open source Java tool for working with PDF documents.
Filza File Manager - Explore files and folders with list view or grid view. View / edit files with powerful viewers.
iTextPDF - iText offers flexible tools for PDF creation, editing and inspection.
Documents by Readdle - A central hub for all your files.
IronPDF - SDK for creating and editing PDFs.
FE File Explorer - The one-stop files solution