Resize pdf dimensions

[crackhammer]

Hello folks,

First of all, not too sure if this is a right place to post this question. If not, mods are free to move to the right section.

Now the question,
In the past, I have scanned loads of books at 600dpi, used ScanTailor and finally made pdfs out of it. I do not have original scan anymore. The size of these pdf is pretty huge and no matter what I do in Acrobat using Resize option, the size isn't getting any smaller. When I look at page dimensions, they are pretty large and practically I do not need such large dimensions of the pdfs.

I wonder if there is any tweak in Acrobat itself that will allow me to resize pdf dimensions or is there any other program that will let me do it on the fly?

Thanks in advance.

(P.S. - Google didn't help much with this search)

[slex]

I don't know about Windows, but under Linux you can do this:

From the command line write:

pdfimages pdffilename.pdf f

You will get the pages from the pdf extracted into files with extension pbm or ppm

then write:

mogrify -format png -resize 50% *.pbm

This will resize the pbm files by 50% and convert them to png. Then you can assemble the png files into a pdf again. You can install gscan2pdf for this.

[DSpider]

Size as in megabytes or size as in pixels? Because Acrobat can resample the PDFs to whatever DPI you want. However, this may not automatically adjust the file size too, because that by resampling you add antialising, which doesn't compress very well. I explained it here (twice):

https://www.mobileread.com/forums/sho...d.php?t=171666

[crackhammer]

@ slex,
Strictly as a Windows user, I don't understand those commands but I can do something similar using Nitropdf, FastView Image Resizer and Acrobat. I have tried it once, I extracted all images using NitroPDF viewer, Resized them using FastView Image Resizer and reassembled using Acrobat. I managed to reduce the file size significantly. The only issue was, if I decide to OCR again, it won't be as good (Its not always needed for my work but sometimes its handy).
The reason, I was asking for a programs that does it 'within itself' is because if I understand correctly when you OCR in Acrobat as searchable image, it 'puts' a layer of text on the image. So I was just curious if it will be possible to keep that 'text layer' as it is and resize the image underneath. Please correct me if I am wrong. There are a couple of programs I found while searching but not too sure how they work.

@ DSpider,
Thanks for taking time to explain the things (twice). The only problem here is, I don't have the original scans to go through the procedure you recommended but I have made a note of it for future scans.

In some cases, my pure goal is to have electronic version of the document/book for backup or quick printing or reading on ipad on the go purpose. I do not need high resolution pdfs in that case. Since I wasn't well aware of scanning issues in the past, I scanned all at highest possible resolution I could afford and work from there. Now after about 2000 books in Calibre, I realize that its wasting space.

I wonder, if I decide to go by the route Slex suggested, what format is best jpeg or png (and no plans of OCR)? I have heard arguments on both the sides in the context of medical imaging (but I didn't understand a word), just felt like those Nikon and Olympus folks were trying to tell me they are smarter than me

[slex]

Obviously, if you reduce the size of the images, it will be more difficult to do a good OCR on the files. As far as the choice of PNG or JPEG goes, if you have Acrobat you can see whether you can use JBIG2 compression on JPEGs - it will decrease significantly the size of your pdf file - making it approximately as big as a text-based pdf.

If you can't do it with Acrobat, there is a program that can do this here:

http://blog.rubypdf.com/2010/10/26/j...pdate-to-0-27/

Note that I use the program under Linux. I don't know how well the Windows version works.

[Sanjay Agnihotri]

Please correct me and sugest if I am wrong – Nowadays, surprisingly at one hand voice recognition is so fantastic and on the other hand OCRs are still hopeless.

Sanjay Agnihotri