This way, you can open the patterns without any problems

The PDF files under "Files / Patterns" at crazypatterns are compressed so they can be downloaded quickly. If you have trouble opening the file, you can download this free program and install it on your computer: www.7-zip.de -

Once the program is installed, all you need to do is unzip the file and save it to your computer. You should also have the latest version of "Adobe Reader." This allows you to open, read, and print the patterns.

But what do I do if I only have an iPad? 

http://www.helpster.de/ipad-pdf-oeffnen-so-geht-s_71746
This page explains in detail how to open PDFs on an iPad.

I think it’s worth mentioning again here: Before you can open the PDF, you’ll need a program to unzip the ZIP file. The link in the original post leads to a program for Windows on a PC. However, there are corresponding programs for all devices (PC, tablet, smartphone) running all operating systems. One example is iZip for iPad and iPhone. That’s what Uncle Google just spit out for me. So you should be able to find suitable software for every operating system (Windows, Linux, Android, iOS) and every device.
Perhaps Crazypatterns should create a list of possible programs, specifying which hardware-software combinations they’re suitable for.

http://www.helpster.de/wie-oeffnet-man-zip-dateien-schritt-fuer-schritt-anleitung_91795