New in Version 4

Soon after Master PDF Editor version 4.0 was released, the developers released two minor updates in January 2017. One significant new feature is the OCR function for processing scanned documents, which is roughly equivalent to the functionality that gscan2pdf [4] or Paperwork [5] attempt to provide. All three programs use the Tesseract OCR engine, which promises reasonably good results.

Using the scan function, Master PDF Editor initially generates a PDF with images (see the "Scanning" box). The OCR function, which you will find in the Document | OCR menu, converts the results back into directly editable PDFs. I ran a simple test to check how well the OCR performs. The idea was for Master PDF Editor to scan a short passage from a magazine and convert it into machine-readable text.

Although the scanner used for this test had a resolution of up to 600dpi, the results were not convincing. The original presented a challenge to the system: The text was not on a white background, the paper of the original was slightly wavy, and the printing was of moderate quality. However, the OCR routine should have identified these problems and correctly scanned OCR text. The results indicated much room for improvement.

Many OCR tools use a more-or-less intelligent spell checker that warns the user if many errors occur; this feature is missing in Master PDF Editor. The installation stores the Tesseract data locally on the hard drive, regardless of whether the files already exist in a system global installation under /usr/share/tessdata/, resulting in data redundancy.

If you want to understand all the features in Master PDF Editor, you can refer to the manual, which comes as a PDF or online [6]. However, it still refers to version 3.7 and thus contains no information on scanning or OCR. That said, the manual explains all the other features well and in detail. In fact, the manual contains a great deal of information about the structure of PDF files that is otherwise difficult to find.

Conclusions

Despite minor weaknesses, Master PDF Editor 4 proves to be a fine piece of software for retroactive PDF editing. In practical terms, no other free software with a similar feature set exists (see the "Alternatives" box). The latest version of the program comes with promising new functions, such as scanning and text recognition, but does not yet deliver in practice what it promises.