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huck999
Participant
December 2, 2011
Question

How to compress a scanned PDF?

  • December 2, 2011
  • 2 replies
  • 191935 views

I am using Acrobat 9 Standard.

I have a 22 page printed text document (no pictures) on letter sized paper.  I had it scanned to PDF.  It is 24 MB.  I have a scan of a similar document that someone else did.  It is 332 KB (roughly 100 times smaller).  Both are perfectly legible.

I have 2 questions:

  1. How can I compress the 24 MB document to make it smaller?
  2. Why did I get such huge differences in file size?  And how can I get smaller file sizes from scans.

In my office I have an HP Officejet Pro.  The HP software scans directly to PDF but the file size is large.

    2 replies

    A
    antonyhill
    Participant
    March 21, 2014

    I notice the same. If I scan directly through the device to USB (it has such option), then document is for some 7 pages of text in 600dpi around 800kb. Scanning from computer results in bigger and uglier images. I guess reason is twofold. First scanning settings.

    Documents from scanner device are much cleaner, I guess there is higher contrast set and perhaps tresholds applied so that text is black and white space on paper is white. Scanning from computer through the same scanner results in subtones in the supposed to be white areas. This makes a big difference IMO for quality of compression later the document is created.

    Another thing is the features of the resulting PDF. See more info here:

    http://blogs.adobe.com/acrolaw/2009/08/reducing-the-file-size-of-scanned-pdfs/

    I guess the scanner (it is actually a MFC device) is using high lossless compression which IMO is perfectly fine for the job. No need for lossless compression for scanned documents.

    MichaelKazlow
    MichaelKazlow
    Legend
    December 2, 2011

    I do not have Acrobat 9 Standard, but I believe you can use the PDF optimizer to shrink the size of the file. The best way to control the size of the file is at scanning time. You can usually control the dpi (dots per inch). Most scanners try to scan at the highest resolution, usually 200 to 300 dpi is sufficient. If there are no pictures scanning greyscale or B & W will also shrink the size of the file immensely. B&W scanning willl always give you the smallest sized file. Lastly, the most efficient scanning is usually done by scanning to TIFF and importing the TIFF into Acrobat. This will give you the best results for text. Some scanner software will scan to jpg and even if scanning to pdf it will use jpg settings which will give the nice results when there are images, but do a poorer job of keeping the text crisp.

    H
    huck999Author
    Participant
    December 3, 2011

    Thanks for the reply.

    I could not find PDF optimizer.  How do you find it?  I didn't find any reference to it in the help file either.

    B
    Bill12
    Inspiring
    December 3, 2011

    Thanks.  It took quite a while to find Optimize.  Not in File>Save As,  Not in Advanced

    Not mentioned in Help

    Finally found it in Document>Optimize scanned PDF.

    It reduced a 24MB file to about 1.5 MB (depends on what quality I specify).


    The location was changed for AA X and that was your problem. A lot of the problems stem from the default use of 24-bit color by many scanners as well as a high resolution. You can reduce the color depth as well as the resolution to reduce the size. Be sure to use Save As or it will save the old stuff too.

    Another option that may require some editing would be to OCR the document. If you do it as a clearscan, it will replace graphic text by an estimate of the text in a font. The editing comes in with the corrections that are generally needed with OCR. The other two forms of OCR do not replace the graphic image, but put the OCR text behind the image -- making the file even larger.

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