The Panama Papers were 11.5 million documents that were leaked all at once -- If a piece of paper is .1mm thick, that stack would be 1.15km tall. If a single piece of copy paper weighs 5 grams, double-sided printing 11.5 million documents would produce a stack that weighs almost 30 metric tons.
Point taken though, one of the bigger stories of the campaign was the billion dollar loss that Trump claimed on his taxes in the mid-1990s. That came to WaPo and NYtimes via USPS and just landed in their mailboxes.
Couldn't one take that many documents and throw them on a flash drive (or even a hard drive if it's on the order of terabytes) and mail that? I'm certainly no security expert but wouldn't the risk in terms of using the drive/files to identify you be about the same for mailed physical media compared to it being sent electronically, but with decreased risk of interception along the way?
One of the things the Intercept recommends as an option is to put your documents in a plain manila envelope, with no return address, and mail it from a public mailbox (not yours, not a post office). But the weakness of this is that they have no way to get back to you.
Would they need to get back to the sender? If so, they could always go the BTK route[0] and address the sender through the paper/website/show itself.
[0] The "BTK killer" asked in an anonymous letter to the police if they would be able to track him down if he sent subsequent letters on a floppy disk. The police took an ad out in the paper to tell him no, they couldn't, so he sent a disk. He wrote the letter in Microsoft Word and using metadata on the file they were able to track the killer down and arrest him.
That's OK for small batches of documents, but even an ordinary court fight between two small businesses can generate hundreds of thousands of pages during the discovery process. Several of my in-laws worked on electronic discovery for the SEC's litigation against Goldman Sachs following the financial crisis, that ran into tens of millions of documents that literally took a couple of years to organize.
