The "Print and Ghost" Problem
You send a draft for a restaurant menu or a brochure. The client says "let me think about it." They print your draft, decide it's "good enough," and never hire you for the final polish.
Browser-Based Protection
SecureViewPDF's viewer uses a custom rendering engine (based on Canvas) that makes printing notoriously difficult. While a determined user could screenshot every page and print those images, the quality would be terrible.
By preventing the native "Ctrl+P" dialog and removing the download option, you ensure that the only way to get a high-quality print file is to pay the invoice and receive the source file.