Change app Version with only IPA file provided (no xcode)
- Rename the .ipa to .zip, and unzip the archive.
- Inside should be a folder called "payload", and inside that folder should be your application archive.
- Right-click the application archive, and choose "show package contents."
- Find the Info.plist file (either named "Info.plist" or "AppName_Info.plist"). Open that file with a text editor
- Change the value of "CFBundleVersion" and "CFBundleShortVersionString" to your desired version number.
- Re-zip the archive
- Rename the .zip to .ipa
- Re-sign the .ipa
In answer to Chris Emerson's comment above (sorry, I don't have enough reputation to add another comment so I'm adding an answer) it is still possible to do this! I have just done it for an IPA with latest updates to everything iOS 8.3, OX Mavericks. I was getting the same message "... could not be installed at this time" and it turned out to be an issue with the entitlements in the provisioning profile not matching the entitlements in the *.app.
You can check the entitlements in both like this: https://developer.apple.com/library/ios/technotes/tn2318/_index.html#//apple_ref/doc/uid/DTS40013777-CH1-TNTAG68, and I put an answer detailing how I fixed the entitlements of my IPA so that they matched here: Alter Minimum OS Version of IPA without XCode, iOS 8+.