This innocent looking 1301 byte .PDF file actually has 2 million pages. The file only has 10 objects, of which 7 are page groups that recursively contain 8 copies of the next page group for a total of 8^7 = 2097152 copies of the same single page.

Firefox and Edge appears to get stuck allocating gigabytes of memory and will eventally crash. Impressively, SumatraPDF actually handles the file very well.

Adobe Acrobat Reader does not render the PDF file, as it does not seem to support having the same Page object used more than once. Checking the specification did not immediately yield a clear answer to whether page reuse is legal. The entire structure is made of indirect object references, and I did not find any indication that an object can’t be reused more than once.