I'm assuming you're talking about the fancy parchment-looking backgrounds and oldstyle fonts. This sort of thing:
If so, let me talk about those for a second, because I have a beef with that mentality. In my experience, those "good looking PDFs" can actually detract from the value of the product. Good presentation is about
efficient communication, not
looking impressive at a glance. These are not paintings to hang on a wall, they are basically technical manuals. Textured backgrounds make it harder to read on a computer screen (for me, at least), and more costly to print. Helvetica on a white background is perfectly appropriate for DM's Guild content.
I disagree that a "good looking PDF" will grab attention. Potential buyers don't see anything except the title, the blurb, and the cover. Those three things (but especially the blurb, which should include a detailed description of the contents) are what grab attention. The graphical quality of the interior pages doesn't matter much, because by that point the poor sucker has already bought it. All they care about at that point is reading the damn thing and seeing if it's any good.
So, I wouldn't put too much effort into making the graphics all shiny. It's far more important (and more impressive) to efficiently and clearly convey the information to the reader, who may have to interpret this text in unfavorable conditions (e.g. reading from an outdated tablet in the middle of running a D&D game).
Not to say that aesthetics aren't important, but I think a lot of DMsG contributors over-value it. Yes, you should make your product look nice. Formatting and layout are very important. But I don't expect professional-looking graphic design from DMsG content. I just want stuff I can use in my game. My favorite purchase so far has been Hex Crawling by neuronphaser -- it doesn't look fancy, but I was looking for hexcrawling rules, and these ones are well thought out and useful. I gave it 5 stars.
/imho
/rant
/this is not necessarily directed at you, but was an important point I wanted to bring up in this thread
/put something up already so i can give you my money