[D-fendr]

There are none in this PDF. Adobe Illustrator probably generates them, I guess.

I'm tempted to say "close enough" on this. But it's more complicated. PDF is Adobe owned and quite complex (it needs to be to work on all systems). Adobe licenses PDF in various ways. Apple, for example, buys the whole thing and, last I recall, Microsoft buys none. Various other vendors can license parts are all or build some kind of converter, etc.

Adobe Illustrator is unique in the PDF world. It is an Adobe product, it can use PDF as its native file format, it works with both vector and raster object and can convert and operate on both.

So, the questions of what Illustrator does or doesn't have to do to a PDF file versus others that license part or all of Adobe PDF is likely quite a ball of wax.

[cartan]

PDF is Adobe owned, but nowadays it is also an open standard (in fact, a coworker of mine is in the PDF/A ISO committee, and I don’t work for Adobe), a well-defined file format. PDF is indeed a very complicated file format, but whether a PDF (or its pages) are multi-layered or not is a simple yes-or-no question. And if Adobe Reader, Foxit, and Inkscape all say there aren’t any, I am strongly inclined to believe them…:-)