You could download it and convert it from Google play, if you have a phone/tablet that uses Android OS. I don't believe you can just download the APK file directly from Google Play to your computer. The instructions are in this thread: playbook android app help please
Get the APK file from your phone
1. Download ES File Explorer from your Google play on your phone. (it is free).
2. Open it up on your phone and click on App Manager (It is the second to last box on the top menu).
3. Find the app you want and hold down the icon unil the Operations menu pops up.
4. Click "Backup"
5. Repeat step 3 and 4 for each app you want.
Put the APK file(s) on your computer
1. Connect your phone to your computer via USB
2. Browse your phone on you computer and look at "/sdcard/backups/apps/" (you may have to turn on "usb storage device" for your computer to recognize your phone.
3. Copy the APK file(s) to your computer
Convert to Bar (my way of doing it on a Mac computer, there are other ways)
1. Visit PlayBook .apk to .bar converter
2. Upload the APK file that you copied to your computer
3. Click the file you uploaded to download it (it will appear after it uploads, under the "Upload APK File" button)
4. Repeat step 2 and 3 for each APK file you copied onto your computer.
Sideload it (again, my way of doing it on a Mac computer, there are other ways)
1. Use Chrome
2. Download this extension: Look for "Playbook App Manager" extension (or use this link)
3. Follow their instructions on screen. If you need help with that, just post and I will sideload an app to refresh my memory on the exact steps.
**Remember to use the converted BAR file on this one. Converting your APK file doesn't overwrite it. The first time I dumbly tried to install the APK file, got fustrated thinking it didn't work, then realized it wasn't the BAR file that I was suppose to use .**
It seems to not be compatible with my device, else I would just download it for you.