PDF conversion and size


I downloaded a PDF from “google books”; It is a 10,5mb file. My goal was to read it using iLiad (a e-book device) but the image compression google used was not good for the iLiad. So, I open the PDF using Osx and try to re-print it using Preview.

  • Using panther I got a 500mb file as result
  • Using tiger I got a 40mb file as result
  • Using tiger and ‘compress PDF’ option, I got a 500mb(!) file

So, the 40mb version was good to me, but I try to use devonthink to reduce more the size. In preferences/OCR i set option for searchable PDF to 120dpi (iLiad uses 120 dpi), 100% quality, and I try to convert the original google PDF to “searchable PDF”. I was not interested in OCR, but only in reduces of dpi images.

After some hours devonthink ends the work (freezing the system, btw), and the result is a 120mb(!) file, with really poor quality in reading. It seems to me that devonthink (or one of itz components) “impoverish” the image during the scale process, even if the quality option is set to 100%.

Is there a way to use devonthink to change the DPI of a pdf, without loss of quality? Why the low-res result of devonthink is 3 times bigger than the hi-res pdf created by tiger?

Thanks in advance.


Apple has changed OS X code for handling PDF creation/viewing several times.

Preview allows one to change the Quartz filter settings when saving a PDF, and it may be possible to reduce the size of a PDF in this way, usually with some visual degradation.

Other applications, including Acrobat, PDFpen, PDFshrink, etc. provide procedures for reducing the size of a PDF. Some work better than others, but there’s usually some loss in viewing quality when size is reduced.

Don’t expect to achieve smaller PDF file size when using OCR with the IRIS engine in DT Pro Office. The image is recreated in the process and almost always swells in file size.

Usually when I scan an document using “import-scan” and after I convert the scan to a searchable pdf, I got a more more smaller pdf.


PdfShrink works now perfect for me - you create your own Template in PdfShrink and define this as “Standart Template”.

From inside Devonthink you may then open/convert/shrink one PDF-File (or a Batch) - right mouse click/open with and PdfShring starts working, using the standart Template. In general I quarter now the Searchable PDFs, created by Devonthink getting a resonable good viewing quality.

For someone who likes to try PdfShrink - my famous settings:

Colour & Grayscale images: 150 dpi, Jpeg 2000, Compression quality low
Monochrome images: 96 dpi, CCITTG4
Fonts. Text & Misc: remove Metadata: not marked, everything else marked
File Output: overwrite original marked - be careful, this will change your original PDF inside Devonthink - so be sure what you do…and that the standart template fit to your quality demands.