The conversion from PPM to searchable PDF can be made by the GUI application VeryPDF Image to PDF OCR Converter and the command line application Image to PDF OCR Converter Command Line. These two OCR Converters can do this kind of job perfectly.
To use the GUI and command line applications, you need to download them at https://www.verypdf.com/app/image-to-pdf-ocr-converter/index.html. When you use the GUI application, please set up it on your computer. When you use the command line application, you need to unzip the ZIP file to some location of your computer.
*Make the conversion with GUI application*
After installing Image to PDF OCR Converter on your computer, you need to launch it by opening the installation folder of the application and double clicking the executable file Image2PDF.exe or clicking “Start”—“All Programs”—“Image2PDF OCR v3.2”—“Image2PDF OCR v3.2”. Then you will see the main window of the application on your screen which is shown in Figure 1.
Figure 1
Then you can do the operations in the application.
Firstly, please click “Add File (s)” button to open file picker window from which you can choose PPM image to be converted and click “Open” button to add it into the file list. After that, you can click the file in file list to see its preview in preview frame above the file list to check whether you have added the right file.
Secondly, please click “Setting” button to open “PDF E-Book Make-OCR Version” dialog box. In the tab control panel of the dialog box, if you want to convert PPM to searchable PDF document, you have to click “OCR” tab and click “Use OCR” option to open OCR status to make the application recognize characters in PPM image. Then please click “OK” button to close the dialog box and the current window will the the former one again.
Lastly, please click “Make PDF” button and click “convert selected 1 file into pdf file” option in popup floating item for opening “Save as” dialog box in which you can choose the location for target file in “Save in” dropdown list and input the name for target file in “File name” edit box. Then please click “Save” button to run the conversion.
*Make the conversion with command line application*
You need to open MS-DOS interface for calling the command line application and input the command line in it. Please press “Window”+ “R” combination on your keyboard to open “Run” dialog box in which you can input “cmd” in “Open” combo box and click “OK” button.
Then please follow the command line template below to write your own one:
img2pdf [options] <-o output> <images>
If you cannot understand the template well, please see the following examples:
img2pdf –x 1 –r 256 –c –o C:\B.pdf C:\A.ppm
img2pdf –x 1 –p 0 –o D:\*.pdf D:\*.ppm
The first example is to convert one PPM the one searchable PDF document. The options in the command line are
–x 1 : create searchable PDF document.
–r 256 : set PDF resolution as 256 DPI.
–c: clear spot in PPM image.
The second example is to convert PPM to searchable PDF in batches. The options in the command line are
–x 1 : create searchable PDF document.
-p 0: append to an exist pdf file and “0” is to insert before first page.
The command line application supports the wildcard character *. Then please hit “Enter” button on your keyboard to run the conversion. Please don’t forget this step. If you want to learn more functions about these two application, you can read the user manual at https://www.verypdf.com/tif2pdf/help/index.htm.