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I'm creating a PDF book from scanned documents and need help optimizing the file size while preserving image quality. Here’s what I’ve tried and the issues I’m encountering:

  1. Current Workflow:

    • ScanTailor Advanced (version 2019.8.16): Processing raw TIFF images with Color Operation options.
    • Adobe Acrobat Pro DC (64-bit): Merging processed TIFF images into a PDF.

  2. Problem:

    • The resulting PDF file size is too large, exceeding 50MB.
    • Lowering the resolution to 100dpi reduces quality too much.
    • Adobe Acrobat Pro DC is very slow at merging images and doesn’t utilize multiple processor cores.

Specific Question:

  • How can I reduce the file size of a PDF in Adobe Acrobat Pro DC while maintaining good image quality?

Additional Details:

  • I need the images to retain their original color.
  • I am open to using Adobe Photoshop if it can help streamline the process.

Any technical advice or specific steps to achieve these goals would be greatly appreciated.

Thank you!

Livre
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1 Answers1

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Because these images have a lot of text you can reduce file size and gain quality by using OCR to vectorize the text. I took your sample PDF which is 6,471 KB and did the following (I'm using 2010-vintage Acrobat Pro 9 on Windows so your menus may be different):

  1. Choose Document>OCR Text Recognition.
  2. Edit settings, set PDF Output Style to "ClearScan", set the Downsample Images to Lowest (600 dpi) to start, set the language to French in this case.
  3. Click Ok to process the document then save it to a new name.

The resulting file is 2,328 KB. Hopefully you can get even better results since Acrobat has had 14 years to refine the process. If you zoom in a lot, say 800%, you may see some text is still pixelated, but most is converted to vectors. In some cases the remaining images that cannot be vectorized may have slight compression artifacts. In my version of Acrobat I can't see an option to control this compression.

The images in your sample PDF already appear to have compression artifacts. Check the output settings in ScanTailor and make sure it's not using lossy compression. It's best to start with a lossless or high-quality scan at a good resolution, say 300-600 dpi. If you still find compression artifacts in the PDF when you first assemble the TIFFs you can change the import settings as follows:

  • Edit>Preferences>Convert to PDF, choose the source image type (TIFF in this case), Edit Settings, then choose something that gives you good results.
User5910
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