PDFtk (short for PDF Toolkit) is a cross-platform tool for manipulating Portable Document Format (PDF) documents. It comes in two versions: PDFtk Free (open source) and PDFtk Pro (proprietary paid). Many functions are not available in the open source version, but only in the paid proprietary one.PDFtk is a front end to the iText library (compiled to native code using GCJ), capable of splitting, merging, encrypting, decrypting, uncompressing, recompressing, and repairing PDFs.