PDF download issue: Apple iOS 12


I am writing this here so that I can send users a direct link to a page on Oz that explains the issue. As best we can.

We've been getting (as of Feb/March 2019 onwards) occasional reports from Oz users asking if there is an issue with our PDF plan files. On investigation, that issue is limited to users with Apple devices, and more precisely, devices that recently upgraded OS, so are running iOS 12.

The problem seems to affect some files, not others. Typically an article file will open, but the plan file will not. Article files of course have a print size of say 10 by 8 inches, while plan files might be say 36 by 48 inches, so are much larger in that sense.

My current theory is that Apple have updated their software recently, and that has broken the way that PDF files (over a certain size) work, the way they are displayed on iOS devices.

As far as we are aware, all Oz PDFs work perfectly on all other devices. So if you have (say) a desktop PC that is not made by Apple, then you will never see this issue.

The really strange thing is this issue appears on new(er) devices, not older ones.

I personally have here 2 iPads, one old and one new. The Old one (Oscar) has iOS 9, the new one (Neil) has iOS 12.

Oscar works. Neil fails. Go figure.

See links below, I spent some time testing this and gathering data. Until shown otherwise, I am calling this an Apple issue. I am declaring our PDF plans innocent.

Meet Oscar and Neil. Oscar is old, Neil is new.

Sadly, we do not have a fix for this issue - apart from simply using a different machine to access the PDF files from Oz. It's an Apple software issue. Presumably Apple will fix it in their own good time. Meanwhile, if you see this issue, we can only suggest using a different (non-iOS 12) device to access the larger PDF files. The PDF files display ok on all other devices.

If you have a failing iPad, but you can get the same PDF file onto your failing iPad through say Dropbox, (rather than Safari) it will also display fine. Because that way it isn't using the core iOS code to render the PDF to screen, it's using Dropbox's viewer. Which is bug-free.

Dropbox and Adobe Reader both work fine, it's the "iOS native PDF viewer" that fails. Above a certain total pixel area. On Neil, that fail number is 350 million.

See my forum posts on RCGroups at for more detail.

Also for test links, more data and success/fail reports.

Got anything to add? then email us.

PDF works fine on Oscar. PDF fails on Neil.

User comments

Really appreciate the article on the IOS12 pdf problem. Thanks!
Larry Jolly - 21/03/2021
FWIW.. I wanted to download Tabi's little Taube to build over the holidays and unfortunately, my iPad still glitches on large PDF's even w/ the latest IOS 17.1.2 I did your tests and 300 kazillion is about it, 350 and it upchucks.. No worries.. I can fire up the PC upstairs if needed.. I'm going to email the clowns at Apple and raise cain.. This problem is well known and we are long overdue for a fix.. Blessings,
AL and 'da hounds - 14/12/2023
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