Can you trust printing to be WYSIWYG at all times?

Can you actually trust that your documents are accurately printed on paper at all times? There is reason to remain critical. Be warned by these examples:

2017: Microsoft Edge shows one thing in a PDF document but prints a completely different thing: “123456” is printed as “114447”. Although the bug was originally reported to and confirmed by Microsoft, the embarrassing bug report now seems to be hidden for public eyes.

2015: David Kriesel revealed in a talk at the Chaos Communication Congress a similar issue affecting Xerox photocopiers, which were replacing random digits in printed documents. Read more on David’s Blog.

Although the Edge and Xerox issues are fixed by now, these cases demonstrate that dangerous scenarios beyond imagination can happen without you knowing it. Sending incorrect invoices to customers is one thing. Printing construction plans with wrong measurements, or life-saving medicine prescriptions with a wrong dosage is something completely different, and most probably will have liability implications.

Issues can be more subtle though. I recall the case of a teacher who used SavaPage to print geometry assignments and found his pupils got confused because, due to a wrongly applied scaling option, the measure of the printed shapes was much smaller than described in the assignment. Luckily no exams were involved, and the defect was easily solved by the current Page Scaling option in the SavaPage Printer Settings dialog.

Bottom line: if accuracy is crucial, carefully proofread a print sample before distributing printed copies to your target audience.

What is your WYSIWYG experience and policy regarding printing?