The Problem: Android Users are unable to view .pdf links in their browsers after opening an SMS link sent to them and see an error message. Why?
The Android Mobile OS was built with a concept called "Intents", which in short means that Apps on the mobile device have specific tasks they handle. For instance, one App can browse the web and open links, but it cannot view files such as .pdf files. This requires users with Android devices to download the .pdf file and have a second App installed on their device with which to open and view the file. This is a limitation specific to Android users, iOS users are able to simply open and view the files in their web browsers.
While this can be frustrating, it's simply how Android is built and there's little we can do to mitigate that.
How can Android users view the .pdf files I send them via SMS then?
It's relatively simple. All they need is an application on their phone to open .pdf files. The link you send them will prompt them to download the file, so they'll still be able to view it. While it may look like there's an issue with the link due to the error message in the web browser, as long as they've downloaded the .pdf file they'll be able to view it just fine.