Note that there's a new iOS app in beta that works with the new PDF reader in the Zotero beta. If you're comfortable running beta software, that will provide the most seamless experience for annotating on an iPad.

I have been using Zotfile for years and the new PDF reader beta, so have some thoughts:

- the new PDF reader will be the smoothest workflow in the end - you'll open within Zotero, read and annotate, and it'll save back.
- However, at present, there are some limits on the beta. The PDFs have to be in your library rather than a group library, and I think it it still requires you to use Zotero storage (although that may have changed). If you have lots of files within Google Drive, then you may have to wait for the beta.
- if you are still trying out Zotero, Zotfile has the advantage of allowing you to use cloud storage to store your files and annotate within those files. This may be more convenient at first if you already have a large file system in a cloud storage folder.
- If you already have Google Drive, you'll also be used to just opening up your files and finding them in your own file structure. If you do a lot of tablet reading, you'll probably be more natural at first at opening them up within your PDF reader rather than through Zotero.
- If you are just reading your PDFs within your own Google Drive, there's really no advantage in sending to tablet over opening them from your Drive and annotating within Acrobat. You can just drag and drop the annotated file back into Zotero and use Zotfile to extract annotations.
- The advantage of sending to tablet is if you imported the file through Zotero itself (eg by using library lookup or the 'find available pdf' option). Then you just use 'send to tablet' to send it to the tablet to read, and send it back to extract.
- I used to do this at the start with Dropbox. As I got more invested in Zotero, I realised that Zotero storage makes more sense in the long term. Zotero storage does store the files in rather obscurely named folders, but the advantage of this is you don't rename or move files so you don't break links. They are just there, and if you need to see where they are located, you can use the 'Show file' option to get to them. If you are a serious researcher, you'll soon find that the search capabilities of Zotero make it much easier to find whatever you want than going through any kind of cloud storage system.
- However, at some point you do realise you have a rather large Zotero database - you will definitely want to change the PDF preferences to download only when needed, otherwise this can slow down your computer.

Assuming you're already very familiar with Zotero + Zotfile, then here is the hint.

When you got hundreds or thousands of files as attachment links in Zotero while they are saved in a cloud drive, they have different hierarchical structures. It could be hard to pick out the paper you want to read within the cloud drive. Zotfile comes help in this situation.

1. Processing your collection to pick some papers to read.
2. "Send to tablet", which is actually to a different directory/folder (let's say "folder-T") that is also synced by some cloud drive.
3. Open in Adobe Reader from that "folder-T". Usually I keep at most ten papers in that folder-T. I recommend to keep this dedicated folder as empty as possible.
4. Finish the reading and "Get from tablet", which automatically extracts annotations you've made on tablet.

So, the trick is that, Zotfile "Send to tablet" speeds up your process when you have large amounts of papers.

In addition, it also prevents you directly interacting with your whole warehouse of papers from any device, which reduces the possibility of crash.