Year is 2367 CE, the invention of teleporter enables an object or even a person to transverse anywhere at the speed of light reliably and efficiently. However just like wiretapping the electromagnetic signals can be intercepted by any crooked individual, with the proliferation of quantum computer data security is virtually non existent in the future. Imagine an insider steals some documents from the R&D archive and teleport himself together with the classified papers right into the wrong hand, this applies even to businesses or individual. I can't block every electromagnetic wave because building such infrastructure would be extremely costly and took up precious space, is there any way to curb tele-hacking? You may assume all teleporters including the portable version can send multiple people depending on power consumption and complexity of parcel, multi cellular organic lifeforms may take hours to scan.
I think the easiest method would be to have your teleporters be ever so slightly crap. They have to be precise enough to safely transport a human being without noticeable alterations and they can transmit a hard drive with a lot more storage capacity than we can store now, but they don't have the precision to read information that is encoded in actual quantum states (as you described being the norm in your world). Thus you can have people teleport (somewhat clunky) data storage devices, but anything in quantum storage is automatically safe. It would be like reconstructing the contents of a vinyl record from a normal photo: the resolution simply isn't high enough.
You need powerful guilds to band together to research and create a framework of DRM spells. There are many commercial interests who find the ability to magically copy a work that they charge money for selling to be a threat to their business model. So they get these DRM spells and use influence to ban investigations of ways to bypass them.
As for teleporting out — not duplicating — a book, or sensitive documents, that’s no different then the problem with any valuable goods, and has been answered already.
Even though quantum computing will destroy current encryption techniques, new encryption techniques are already in the works for if/once quantum computing takes over. So data being transmitted via teleportation will likely still be encryptable in the quantum computing era. Thus if a group hijacks a teleport they will likely end up destroying the item being teleported (small comfort if it was a person being teleported).
Insider threats do not need teleportation to be a threat. Insider threats are considered trusted and abuse that trust to steal information. Insider threats can easily walk the data out the front door or perform a legitamite teleport with the data.