PDF (I am waiting for urgent answer and solution)

Question

It is very difficult to open pdf files from a mobile phone, after reaching a certain page, almost all blank pages appear, not openedWhat's the solution?

Dov Isaacs · Accepted Answer

I corresponded to user Adam-2000 offline two days ago. He shared some of his problematic files with me and with my usual dilligence, found out what was really going on.

(1) The files also render slowly with Acrobat Pro DC on my desktop system with Xeon processor, tons of very fast memory, souped-up video card, and SSDs. They render much slower on my iPhone 11 Pro Max and iPad Pro. I can only assume that they look like they are hanging on older, much slower mobile devices.

(2) For the file I examined in detail, I found that behind the text of pages beginning around page 22, there were multiple layers of transparent raster images, JPEG2000-compressed, and with a Pantone spot color channel. Since the text was knock-out and opaque above the background, it did not contribute to the complexity and thus the rendering performance of the document.

(3) I performed a number of steps using Acrobat Pro DC to yield a file that rendered very quickly without any loss for purposes of display. I converted the Pantone spot color to process CMYK (the background raster images were DeviceCMYK already). This would only be an “issue” if Adam-2000 was actually going to print to a device that actually had that spot color (which wasn't out of typical CMYK gamut, by the way), I then flattened the PDF file's transparency and in the process ended up with regular JPEG compression instead of JPEG2000 (JPEG2000 compression has performance issues both encoding and decoding due to the more compute-intensive nature of the compression algorithms). The original background images were 150dpi and I made sure that the final background image was 150dpi.

The resultant PDF file displayed without any performance problems on my mobile devices - not as high performance as simple pages with no background from a Word document with no graphics - but quite acceptable.

I e-mailed the resultant PDF file back to Adam-2000. His response back to me is that “he can't understand.”

There isn't anything more that Adobe or I can do for Adam-2000 since the problem was really that of the original content and not taking rational steps to simplifly same for production.

Dov Isaacs · Answer

Adam-2000,

We have done due dillegence in examining one of your PDF files. As indicated above and in my detailed response to you via direct e-mail, the performance issues you are encountering with your PDF files have to do with the complexity of those files and attempting to view them on platforms that often have much less resource than a desktop computer.

I provided detailed information to you as to the source of the problem in terms of the multiple layers of transparent images with a spot color chanel beneath your text. Flattening those multiple transparent images down to a single full page opaque image and placing same in InDesign, with the spot color output as process, would dramatically increase viewing performance.

I also provided details in that e-mail as to how I used Adobe Acrobat Pro DC's Print Production tools to “fix” the slow-rendering PDF file after the fact.

For better or worse, neither I nor Adobe, nor these online communities are in the business of fixing customer files “after the fact.” In my e-mail to you, I outlined exactly what I did in Acrobat Pro DC to “fix” one such file using a number of the print production tools available therein. It is now your responsibility to fix the other files preferably by fixing the source per above or by doing an after-the-fact fixup in Acrobat Pro DC. If you choose to hire someone to do this work, expect to pay for up to several hours worth of time to complete the work.

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