A quick scan of the various app stores and it seems like there are more PDF viewers for mobile devices than there are for desktop machines. With the relatively recent entrance of Adobe Reader for Mobile, I thought it might be a good idea to come up with some recommendations for designers who create PDF documents and want to ensure that they display predictably on mobile versions of the Adobe Reader. But PDF files don’t actually need to be created specifically for mobile devices to work well on them. My recommendations are more about how to prepare your files to take better advantage of the limited feature set available in the mobile versions of Adobe Reader while providing a good experience for dynamic PDF files on the desktop.
Reducing the File SizeIf you think your audience might be reading your PDF file on a mobile device, the first thing you might think of doing to your PDF file before distributing it is to reduce the file size. It’s a good idea but there’s a right way and a wrong way to do it. You don’t want to use the File – Save As – Reduced Size PDF method in Acrobat X. This method removes the Standard 14 Fonts from the file, assuming that they are present on most desktop machines; for mobile devices, this isn’t a great idea. Instead, use PDF Optimizer for finer control over what get’s removed; more on that later. First, be sure all the fonts used by the document are embedded so it will look right on mobile devices.
Font Embedding:You’re going to want to be sure you’ve embedded any fonts used in your document even if they are normally present on a desktop machine. Embedding fonts prevents their substitution and ensures that your audience sees the text in the original font. Embedding increases file size… slightly… unless the document uses Asian language fonts, which can be several megabytes. You can embed the entire font, or just a subset of the characters used in the file – which is what I recommend.
To be sure your fonts are embedded, Choose File Properties then click the Fonts tab in the Document Properties dialog box.
If a PDF file uses fonts which are not embedded, you can embed them using the “Embed Fonts” fixup in the Preflight tool; you’ll need Acrobat Pro to run Preflight. The fonts you are embedding must be present in the system’s font folders though some fonts may have a permissions flag indicating that their license does not allow embedding. In this case the fonts are not actually embedded into the PDF file.
More detailed information ca be found in the help document in the Preflight tool section. Look for the “Embed Fonts” fixup in the “PDF fixups” category.PDF Optimizer
Create BookmarksAt the time of this writing, links don’t work in the mobile Adobe Readers, though they do in Preview and iBooks on iOS devices. At first I was a little confused as to why Adobe decided not to make links work; then, as research for this document, I tried using iBooks with a PDF file that had table of contents links… Ouch… I’ve got fat, little, sausage fingers and the number of times I had to tap my iPad to get to the right link was really annoying. Additionally, when I clicked the wrong link and went deep into the document, there was no “back” button to easily return to where I was and try again. My conclusion, while the Adobe Reader for Mobile doesn’t implement links, you’re not really missing anything. Even on an iPad, typical links in paragraphs of text or a ToC are just too small to be useful. Instead, add bookmarks to the more interesting locations of your longer documents.
File NamesAt the time of this writing, PDF files are not indexed by either Android or iOS devices so you’ll want to use meaningful file names when saving your files, the document title metadata field is not used at all by the mobile Readers. Your audience needs to be to easily identify the PDF file they are looking for based on just the file name alone. This is the kind of thing that is actually good practice anyway; it improves SEO, even for PDFs.
Meaningful file names are most important for the attachments in PDF Portfolios. Files are listed by filename rather than the “Display Name” metadata field and are always displayed in alphabetical order; the sort order defined by the Portfolio is completely ignored. If the order of your files is important, you need to use numeric prefixes for your filenames when placing them into Portfolios. Now – the good news here is that you can still have nicer looking names in your Portfolio with the desktop Reader since the display name is completely separate from the filename and is used by the desktop Reasder.
TaggingAndroid users have it slightly better than iOS users (there’s a loaded statement). Adobe Reader for Android can reflow a PDF if it’s tagged. On Android devices, press the menu button and use the reflow “View Mode” to view documents in this way.
Tags in PDF, just like XML, are used by assistive technology to help people with disabilities read the document. Because they define the proper reading order they can be used by the mobile devices to reflow the document. Microsoft Office, Adobe InDesign and Adobe FrameMaker automatically create tags when you create the PDF via the PDFmaker. If you’re another product to create your PDF files, you can use Acrobat to add tags to your documents. By following the accessibility guidelines, you’ll create a PDF file that can be easily read on a mobile device.
Unfortunately, iOS users will need to wait on this pretty awesome feature.