I just used metapdf for the first time on a mobile device (windows tablet, since that’s the only thing working at the moment) and I noticed that compared to the old pdf viewer, metapdf is incredibly slow on underpowered machines like this.
Makes sense, lot’s of nice features need power. I just want to know if you plan on optimizing the app on that front until dedicated mobile support comes around.
MetaPDF was never meant to run on a mobile device. There is a reason why we show a big warning when you try it 
There are dozens of dedicated PDF annotation programs on mobile (unfortunately only relatively few with good Google Drive support).
We will definitely try to optimize the App for performance. Actually we do it all the time. However, there are limits at the moment how fast a PDF viewer can be in a browser. The PDF viewer of Chrome is not a webapp like MetaPDF but a “native” app embedded in the browser, which will always be faster. Paperpile will always support opening PDFs using this viewer for the fastest possible performance.
MetaPDF is proving to be a massive drain on my computer, in terms of the CPU and by extension battery life on my laptop.
As an example, my CPU is currently running at about 3-10% usage (and RAM at about 40%). Now, if I open and start using MetaPDF, CPU usage rockets to 50-65% (and RAM at about 55%).
Is this likely to improve in the future?
Is this for a specific PDF? Clearly if it’s a PDF with hundreds of pages and all are bitmap images it will take more resources.
Typically, you should never have constant CPU load just because you have a PDF open. If that’s the case that’s a bug. We would need more details to find out what’s going wrong there.
The limiting factor is the underlying PDF.js rendering library. It improves all the time so going forward things should get better. And if it’s a problem with MetaPDF itself we will do our best to fix it (it’s still in beta for a reason…)
It was a small PDF (500KB), with no images. It happens whenever I use MetaPDF, but only when the tab is open. As an illustration:
I noticed meta pdf consumer many resources too. But I had a 500+ page PDF open. I left for lunch and came back and my laptop was hot (forgot to sleep it) … realized it was from MetaPDF. That’s the kind of heat my computer generates when gaming, streaming video, or running a big analysis.