Display PDF in android device

[MaxV]

Please note that on Linux (and so on Android and Mac) there are symbolic links.
Linux ALWAYS mount in the /mnt directory. So /mnt/sdcard should always exists.
Go to /mnt and see what it contains, probably there are:

• sdcard (virtual internal sdcard)
• sdcard2 (real external sdcard)
• extsdcard (real external sdcard, a link to sdcard2)

Your folder /storage/extSdCard/ probably is just a link to /mnt/extsdcard.
See:
http://en.wikipedia.org/wiki/Mount_%28Unix%29
http://en.wikipedia.org/wiki/Ln_%28Unix%29

[SparkOut]

Yes, that's what I was driving at - I know from browsing around my devices there are several permutations of paths to storage, with a variety of symbolic links to the different places storage/sdcard0 versus /mnt/sdcard etc.
I was hoping for some definitive location across all android versions and devices...
Maybe a specialFolderPath("storage") would be possible?

[MaxV]

No, since there is no standard.
I suggest you to use /mnt/sdcard, it's always present, no matter if it's a link, an internal virtual memory, external memory, etc.

[SparkOut]

Well thanks, that was helpful. Delving into the folder structure without root, file managers still managed to give inconsistent paths and symbolic links, also changing whether the phone was connected to the computer or not. But even though it's not one of the paths consistently displayed by file managers, using /mnt/sdcard/ is working, so far solidly in all situations.
Big thanks