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I have a pdf that is very very slow to load/display. It has transparency like layers I believe(because a partial layer is rendered first then another layer seems to be rendered on top). It is rather high quality.

The file is small at around 75KB/page. I have tried to optimize the pdf, reduce file size, and export to various image qualities such as jpeg, png, and tiff.

When I export to png at a very high dpi the png is 6MB and has near the same quality as the pdf but is almost 100 times larger. I have done a jpeg at around 200dpi that is about 10 times as large but an obvious loss of quality.

I do not understand why I can't get a similar quality and page size when exporting the pdf.

If I do 300dpi jpeg with low quality compression I get a similar quality image but still almost 10 times as large of a file but it does render much faster(at least in ifranview).

The pdf is just basically monochrome text except for some gradient like blur effects on edges of font but does have artifacts from scanning which pick up the image on the other side of the page.

I know for a fact that the issue is from the method of scanning(possibly the software used) since I have almost an exact copy from some one else that is much faster(although the file size is almost 2x). The other copy does not have the "transparency" like layering thing when rendering. Hence, my guess is someone scanned this pdf and used transparencies as some option which screwed up with the pdf. Acrobat doesn't seem to make it easy to get rid of them. All the optimization stuff does not remover or correctly flatten the transparencies.

When optimizing the pdf I do see "flattening" in the progress bar box. If I save as a ps file it is 100 times as large and much worse quality in ghostscript. When then using distiller to convert that back to pdf I get a new pdf with near the quality of the original, loads faster, but about 15 times as large!

Now realize, I'm working with only 4 pages, the original pdf is really 1000 pages and about 50MB, if I save that to ps then it will explode to about 5GB(assuming it linearly scales). Converting back to a pdf will reduce that to around 500MB and probably take a few years to complete.

So, what the heck is going on? It seems that transparencies are at the heart of the matter but I can't seem to get rid of them(flatten them) and they seem to help in reducing the file size for some reason. (I have a very similar pdf that is about 2x the size without transparencies or slow rendering and I'm trying to achieve the same effect)

I know there is not a lot of specific information but I can't upload the pdf's since they are copyright...

share|improve this question
After doing some OCR in ABBYY I noticed that the result also seemed to have "layers" when rendering and is very slow. It is possible that the pdf was scanned and ocr'ed(Even though there is no real text involved). – Archival Dec 31 '12 at 18:37
Not sure how "The pdf is just basically monochrome text" fits with "there is no real text involved". “Optimized" layout can be expected to consume more disk space than linear. I doubt I could answer your question but an example might help someone else to. Is there are a chance of uploading even a single page somewhere accessible, maybe an inserted one with innocuous text then copied out again? Are you able to revert to source and ask them what export options they chose? – pnuts Jan 12 '13 at 16:00

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