It was 2015, and Trump campaign chair to-be Paul Manafort had a problem. For years, he’d been flush with cash paid by Ukrainian president Viktor Yanukovych for his firm’s consulting work. When Yanukovych fled to Russia in 2014, however, that money dried up.

According to special counsel Robert Mueller’s latest indictment (pdf), Manafort’s savings were illiquid, hidden offshore in Cyprus, and he didn’t want to bring them onshore legally and pay taxes on them. So he and his then-number two Rick Gates (later a fellow top Trump campaign aide) allegedly cooked up various schemes to use US properties, which Manafort had already bought with offshore funds, as collateral for loans from US banks.

First, they had to convince banks that Manafort’s firm was still raking in money, explain Mueller’s charges. So the pair doctored profit and loss statements to claim that in 2015 that they had earned $4 million more than they actually had, and $3.5 million more in 2016, the indictment alleges. But doing that involved a technological trick that has vexed many a computer user: changing a PDF file into an editable Word document.

Manafort, it seems, couldn’t get his head round the conundrum, but Gates—23 years younger—knew what he was doing. Their skill exchange created a potentially incriminating paper trail: Manafort, then 66, emailed Gates a 2016 profit and loss statement in PDF form, which showed a $600,000 loss. Gates then turned it into a Word document, the indictment says. Manafort edited the resulting document, topping up the balance by $3.5 million and sent it back to Gates to turn it back into a PDF. Manafort then allegedly sent the doctored file off to an unnamed bank for a loan application.

The bank apparently didn’t see through these shenanigans—or didn’t act on them if it did. Mueller’s indictment says that bank gave Manafort $16 million in two loans between July 2016 and January 2017.