PDF annotations are in beta. Please read this first

MetaPDF is our new web-app to annotate PDFs in Google Drive. PDF annotations are also useful beyond academic literature, so we decided to implement it first as a standalone app which will be fully integrated into Paperpile soon.

MetaPDF is in beta and we welcome all Paperpile and MetaPDF users to share their feedback with us in this forum.

Getting started

Sign up for MetaPDF here: https://www.metapdf.com

You can also install the App from the webstore:


Feature highlights

  • Annotations are saved natively in the PDF and can be read and edited by any standards compliant PDF program.
  • Annotations are synced back transparently to Google Drive.
  • Fully collaborative. Annotate PDF in realtime together.
  • PDFs are processed locally, i.e. the PDF is never transferred or stored on our servers.
  • Properly displayed highlight annotations that are not overlays over the text but “painted” natively on the page.
  • Streamlined UI with keyboard shortcuts (e.g. select text and try pressing 1,2,3,4) and full undo capabilities
  • Markdown support in annotations
  • Beautiful, printable summaries of all annotations in a file
  • More to come…

Roadmap for Paperpile users

Step 1: Initial release as standalone app without sharing and collaboration.
Step 2: Sharing and collaboration.
Step 3: Allow opening PDFs from Paperpile in MetaPDF
Step 4: Integrate MetaPDF as Paperpile branded viewer in Paperpile.
Step 5: Show highlights and notes of PDFs in Paperpile.

Known issues

  • Although it’s possible to print documents and annotations, we are aware of a few issues and hope to make printing more robust in the future.
  • Some functions are not yet available on Safari (fullscreen annotations view, printing).

Whats new in Beta 3

  • Support for Firefox and Safari
  • Page rotation
  • Show recent files list on startup screen.
  • Many bug fixes and minor improvements.

What’s new in Beta 2


  • Privacy: Fewer permissions are required (the app now only requires access to files uploaded via MetaPDF)
  • MetaPDF can now be installed via the Chrome Webstore
  • PDF files can be opened directly with MetaPDF from the Google Drive Webapp or GMail
  • Reloading of the tab will actually reload the document
  • Linkable URLs via app.metapdf.com/g/[gdrive-id],
  • Undo for all actions
  • Many more small fixes and improvements

Saving and syncing

  • Real-time saving of all changes that will be restored in a new session even when they have not been synced back to Google Drive
  • Automatic sync to Google Drive is now optional (useful for large files).
  • Check if file has changed outside of MetaPDF and ask the user if she wants to keep the version open in MetaPDF or the externally changed version in Google Drive.

Collaborative features

  • Files can be annotated collaboratively in real-time
  • Files can be shared with other users right from within MetaPDF
  • Other users can reply to comments.


  • Annotations list panel can be resized and hidden
  • Width of “Sticky” notes can be adjusted
  • Comments only show author details if multiple users have added comments. That saves space for the major use case when only one user annotates a file.
  • File can be dragged to MetaPDF right from the Chrome download bar
  • Always show current page number and total number of pages
  • Fixes for zooming
  • Improved recent files list (files that are not present in Google Drive anymore when opened will be deleted from the list)
  • Various new keyboard shortcuts


  • Full screen annotation view
  • New color scheme for highlights
  • Markdown support for notes
  • Print document with and without annotations
  • Export annotations in Text, HTML, OPML and JSON formats
  • Improved text extraction from highlights

Hey, love the potential here. Any clue when the next version of MetaPDF will be out? Any clue as to when you guys will merge this with paperpile? dying to know

We have just integrated MetaPDF into Paperpile. Check out this post for more information on how to annotate and highlight PDFs directly in Paperpile: Highlight and annotate PDFs in Paperpile

Really glad this has now happened, it will be incredibly useful.

However, I’ve just been experimenting with highlighting text and then printing the annotations, and I’ve noticed a small niggle which hopefully you can fix.

The vast majority of the text that I highlight then appears in the left hand column without the spaces between the words, which makes it difficult to read afterwards.

Thanks for all your hard work, referencing has been so much easier since I found you!


Could you, please, send one of these PDFs to andreas@paperpile? That would help a lot in debugging.

When you double click on the items in the left hand column, the text becomes editable and you can add spaces.

Please be careful when implementing the new annotations, because right now with the old viewer, we can search text within our annotations right from the google docs add on.

Please be sure to add this spec in the new viewer and annotator (make the add on capable of search within the notes we made as readers please)

For me OPML export does not work. I think the hyperlink for the button, needs to be fixed (clicking does not change anything).

If Paperpile eventually allows offline annotations and syncing of those annotations upon going online again I will be entirely sold. I would love to be able to read and annotate papers on my tablet while out and about. Love the product! Great work.

Hi, I am using MetaPDF through GoogleDocs but somehow the comments text has been converted to unreadable character mapping like this:
:<:<<;; << <<;<<<<;;;, <<; <;:<;< (;;. <;<;;:<<)

Also getting an unable to syc message:
Could not save annotations this type of PDF file. This should not have happened.Please contact

Can you please help retrieve my comments? I have also sent a message to support with document link.

Overall the MetaPDF seems pretty solid, but there are a few annoying issues:

  1. If I accidently delete a comment, the undo (ctrl + z) does not bring the comment back. MetaPDF says “Cannot undo, the annotation was deleted by another user”.

  2. If I want to quickly copy n paste something in the document, I need to first deactivate the “markup mode” or else I end up marking up the text I intended to ‘copy’. I think it would be easier to utilize ‘right click’ to markup the document after highlighting.

  3. On the left side-panel, it would be nice to have the ability to delete comments or annotations. (My document has some annotations that I see in the left side-panel, but I can’t find them in the PDF, and therefore can’t delete them.)

  4. The right side pop-out for comments is a bit annoying. I’m using a vertical monitor for my PDF’s so I have very little screen width. When I click to comment, the PDF shrinks to allow space for the comment. I think it would be better to just overlay the comment on the PDF so I can keep my PDF 100% width of my monitor. (Like how comments are handled in Adobe Acrobat)

That’s it for now guys.

I’m a longtime PaperPile user; I was one of your initial beta testers, years ago. I discovered MetaPDF through PaperPile when I discovered that all of a sudden the PaperPile default viewer allowed annotations. I was blown away – I’ve waited years for this, and has made my PaperPile experience complete. This is literally the FIRST TIME that i have been able to annotate (and read other people’s annotations) on PDFs on my Chromebook, and have them saved to the original PDFs in The Right Way… I used to have to go to a Mac to use Preview, or go to a PC and use Adobe’s awful paid app, to do anything non-trivial with PDFs.

That said, I also love it that MetaPDF is available as a standalone app. Since discovering it in PaperPile, I have used it to annotate things that I would not normally import into PaperPile (like conference programs), and to read annotations on things that I not ready to import into PaperPile yet (like reviewer feedback on manuscripts I have submitted).

So, basically, thank you for MetaPDF! I see that shapes, text boxes, form-filling, signatures, and page management are on your development list. I applaud this: at that point MetaPDF will be able to everything that MacOS Preview (and the paid Adobe app) can do, but on the web and for free… though I would probably be willing to pay. If you’re collecting data about user priorities, I would use form-filling the most often, followed by page management (though there are several free-but-clunky web apps out there for merging and splitting PDFs). Shapes and text boxes are lower priority for me, as are signatures… and there are some decent (paid) apps out there that do online PDF signatures.

Hi there, I’m quite satisfied now with the pdf viewer (much faster and stable than before :wink: ).
My suggestions are:

  • search text should highlight all matching words (currently only 1 word per page is highlighted). This is very very annoying for me…
  • Sometimes the search is buggy and doesn’t display anything… I have to reload the page and search again.
  • search less than 3 letters would be nice

Will this feature ever be finished and come out of beta?

hey, I really need the ability to print annotations - you used to have this feature - what happened to it???

This was reallyuseful THANKS :smiling_face_with_three_hearts:

Is there an ETA for the last 3 features that are scheduled to be added? For me, having those would make subscribing to Paperpile worthwhile. Otherwise, Mendeley can do most of what I want.

Bom dai!
Como faço pra ter acesso ao leitor de pdf beta? Sou novo e não consegui acessar nenhum recurso que inclua leitor de pdf e app android!

Any news on the development of this feature??

1 Like

Hey everyone! I come here every couple of months to check on the status of this, but I just wanted to say that if this pdf-highlighting feature is important to you, to check out Diigo.com

Given what it’s capable of, I’m super surprised it has such a small following. Take a look and lemme know whatcha thing if you’re so inclined ^^