Publisher reducing pdf size

[Gianni Becattini]

Hi,

I am trying to export a book I wrote for print but I am not able to reduce the pdf to a reasonable size (it is now many giga). The book has about 600 pages with a lot of images; many of them have a very high resolution (up to 700 dpi and more); all of the images are Affinity Photo documents.

If I set the downsample images option, the size does not change at all, even if I set a very low value.

I am using a small file for the tests, with just few pages.

Could someone please help me?

[MikeTO]

Hi Gianni, I just tried it and couldn't duplicate the problem. I tried it with afphoto and tiff files and in both cases, downsampling led to a much smaller file.

What are your export settings? Would you be able to share a test afphoto file?

Good luck

[R C-R]

1 hour ago, Gianni Becattini said:

The book has about 600 pages with a lot of images ...

About how many images in total are there? What 'downsampling above' values have you tried?

[Pšenda]

Exported Image is with metadata and ICC profile? 

[thomaso]

4 hours ago, Gianni Becattini said:

If I set the downsample images option, the size does not change at all,

• What is your document / export resolution? Is it 700 DPI, too?

• Did you set a downsample DPI limit only, or did you also activate "Allow JPG compression" and, if yes, with what value?

[Gianni Becattini]

First, thanks for replying.

I could somewhat proceed and I can give you the following information:

• I want to export with 300 DPI maximum resolution;
• I don't know exactly how many photos I have, maybe 700-800.
• I want that higher resolution images are downsampled to 281 DPI (for test)
• my settings are as shown in attachment
• the problem does not change if I use single files instead of a book;

Using Acrobat, I could check the document and see that most of the images are at 300 DPI, as requested, just a few (about 20 or 30) are at higher values.

I used a small program (PDF squeezer) to reduce all the images to 300 DPI and it worked; but with a saving of only 3-4% in size. So I am beginning to think that the problem is without solution, even if I could convince AP to do its job correctly...

[thomaso]

One of your two screenshots did not upload properly, so you might want to edit your post + delete the text link + upload the missing screenshot once more.

5 hours ago, Gianni Becattini said:

• I want to export with 300 DPI maximum resolution;
• (…)
• I want that higher resolution images are downsampled to 281 DPI (for test)

This "to" appears to be a misunderstanding. The option "Downsample images Above" is meant to affect images that have an effective resolution in the layout of more ("above") than this set value ("281"). Means, images with a resolution below this value will not get downsampled. From this perspective this value does neither set the final export resolution (which you have set to 300) nor does it upscale images with less then 300 to 281. Accordingly this "above" value should get set above the value you have set as the wanted export resolution (300).

While this "Above" setting at 281 does not increase the exported file size (or export resolution) the compression quality setting of "98" is more relevant in this sample. Reducing this value will result in larger differences of the exported PDF file size. A comparison of a page with a few sample images with an export quality setting of e.g.  72 | 85 | 98 will show that the difference in file size between 98 and 85 is higher than the one between 85 and 72, although the set quality values differ in the same 13 for each.

Depending on the colour profiles of the placed resources in your layout document also the export options "Embed profiles" and "Convert image colour spaces" may matter and influence the resulting PDF size: Unticking the embed option and selecting the convert option may reduce the export size, too.

[Gianni Becattini]

Thanks for replying. I have removed the wrong attachment, but it still appears as empty, I don't know how to do.

For the rest, I agree with what you say. The point is that sometimes it seems not to work as it should. If I say "downsize above 300" I expect to have no image in the file with a DPI more than 300, but I find in the pdf file images much above that (e.g. 700 DPI).

Currently I am repeating the tests, I don't want to affirm something wrong, I will be back.

Thanks again.

[Gianni Becattini]

Maybe I understood something (still not sure). The problem could be due only to my dumbness. When you set the "above" field, you must press tab (or some other key), otherwise it is not accepted and it remains to the 375 default value.

Proceeding with greater care, I generated a file where no image is above 305 DPI (Acrobat has a way to check all this by pressing Cmd+Shift+X and configuring the checking accordingly). I will confirm as soon as I proceed.

[Gianni Becattini]

I confirm my last post, so my fault, sorry!

Thanks however.