PDF annotations private beta 2


We were aware of this app and some open source projects named metapdf. But names are a limited resource these days and none of the other metpadfs seem to be serious enough about their brand that they bought the .com domain. So we went for it.


#Comments on paperpile pdf app

  • would be nice to have hotkey hints on button mouse-over of the annotation and commenting buttons (like the hints you get in the color dropdown menu). I usually forget these things
  • already mentioned elsewhere: reloading the page clears the pdf viewer and the file has to be re-selected
    • would be nice to have an overview of the last files (maybe as tiles). The last modified overview is not specific enough
  • after reloading a pdf with annotations (opening it with the annotations) the highlighting is still rendered correctly on the text but the annotations in the right column is initially missing, they seem to reappear when I am scrolling for a bit. Also, the page view is reset to automatic so if I collapse the side panels the page is not expanded


  • having the in-browser fullscreen view of the pdf (both sidebars hidden) to maximize laptop screen space makes it impossible to add annotations because the annotation field is hidden. It would be better to have it
    1. pop up even in fullscreen
    2. not require an additional mouse click to gain focus after clicking on the annotation icon.
  • after highlighting text, it immediately loses focus. So in order to change the color after
  • Annotations cannot span multiple pages. Once you cross to the next page, the entire next page get’s highlighted.
  • The highlighted text in the left sidebar should be collapsible (showing only the first line and then …) and if there is an annotation associated with it, contain both the highlighted text and the annotation. Maybe this could be solved like the abstract and note view in paperpile which you can expand when needed. There could be a button on top of the list to expand/collapse all annotations/text selections.
  • Also, having a way to sort highlights by color would be nice as I believe most people will use the colors for different types of highlights (at least I do)
  • The ‘general annotation’ field (free text popup) of the current paperpile pdf reader is actually quite useful for unspecific thoughts and ideas. Would be nice to have that also in metapdf.
  • The browser window seems to lose focus after deleting an annotation. At least the hotkeys (1,2,3,4 for color selection) only work after clicking on the pdf again
  • Annotations in the right sidebar should automatically adjust their size according to text length. This is not a major issue as you can do it manually but it would be nice if they expanded on focus and then collapsed on de-focus.


I just wanted to pop in and let you know that this is exactly what I’ve been wanting. I’m just starting to get this integrated into my workflow, so I’ll hopefully have more specific feedback soon.

Since this looks to be a separate products, are you planning to charge extra for it or include it with a Paperpile subscription?


Noticed a strange difference in the fonts when viewing in the MetaPDF vs PaperPile viewer. It’s exactly the same file. Tried it multiple times including closing Chrome and reopening too.


Hi there,

I had noticed an issue with the highlights and underline for a “Nature chemistry” paper: they would not be centred on the selected text.

This has since then been fixed, thanks!

Recently I noticed the same problem with “Journal of Medicinal Chemistry” papers. See the screen grab where I had selected the word “rigid” to be highlighted. And here’s a link (behind a paywall, sorry) of the paper in question. http://pubs.acs.org/doi/abs/10.1021/jm050565b




I wanted to stop by and say that I am thoroughly impressed, and this app has exceeded my expectations.

Features I Love##

  • Keyboard shortcuts
  • Annotations also function as bookmarks
  • Annotating after I have selected some text (rather than having to click highlight, then select text)
  • Integration of bookmarks! (many viewers don’t allow this for some reason)
  • pressing ‘del’ deletes an annotation from the document or the sidebar

“Would Be Nice”

  • keyboard shortcut for “hand” tool & comment
  • Somehow integrate citations into the comments sidebar
  • you could click on a reference and add that article to Paperpile
  • avoid scrolling to the bottom of the article to see the title of the cited article
  • add a Paperpile label to a document while viewing; create a label from selected text


Y’all have done an excellent job. I was only expecting some basic features, but this looks/feels better than many of my standalone readers (Readcube, Mendeley, etc…) I have not experienced any bugs or cons as of yet, save for the obvious features that will be enabled once it is fully integrated into Paperpile. Thanks again & I’m looking forward to the final release!


Thanks for the detailed feedback. You will love the new version which should be much more stable and have more features.


Tried it out today. Most of the features work well though have been experiencing a bit of lag when large blocks of text are being highlighted (something like 2 -3 paragraphs). Also in case the annotation covers a large block of text the edit options for the highlight appear lower down instead of following the cursor position. So you may have to scroll down a lot in order to delete the highlight made.


I am loving this over notablepdf on my chromebook right now. I hope there’ll be an ability to rotate pdfs in the future within metapdf, though. It’s a little annoying to have a prof upload a scan of a book that’s sideways and I can only rotate it in notablepdf and chrome’s default pdf viewer. I have tried to save from both after doing so and it still opens with the original orientation in metapdf. I love using it on the files that I can, though!


As far as I know we’ve implemented rotating already and it should be part of the next release. @andreas can you confirm this?

Could you elaborate what exactly you prefer over notablePDF? It would help us better understand the strengths of our product.

In any case, thanks for testing and your feedback!


I had the same problem today with a journal called Psychonomic Bulletin & Review (doi:10.3758/PBR.16.1.88) published by Springer.

– Mark


I just saw the same thing and I believe one cause of it is when you zoom the PDF enough to be able to scroll it horizontally. Tested without zoom and the highlights looked fine, then tested with zoomed in and scrolled “right” (so the text went left) and the highlights were mismatched but only visually.


Strange issue. When I choose “page width” from the zoom menu I get a blank screen, as if the back button was clicked, sending me back to the new tab view. I have to forward-click to get back to the app and I’m no longer in the document view, but at the top level. Is this happening to anyone else, or maybe it is a conflict with one of my other plugins?


That’s a mysterious bug. @Lukas_Endler described the same above. It’s some weird manipulation of the history done by PDF.js the underlying library we are using. We should get this under control soon. Thanks for reporting.


I’ve also noticed behavior along these lines, where the text renders differently in Meta PDF relative to the default viewer. In particular, I’ve noticed that the text is not as dark and crisp in Meta PDF. Perhaps this is unavoidable consequence of introducing annotation?


The underlying PDF rendering engine is completely different. So differences will be unavoidable. You also get differences when you view a PDF in Acrobat vs Mac Preview for example.

We use pdf.js as the rendering engine for our new viewer. There are clearly tradeoff bringing such a complex thing like a PDF viewer into the browser. But pdf.js is state of the art used by millions of firefox users every day. And it’s moving fast so I think it’s a good choice to base our annotator on (and it’s the only choice actually…)


I am liking this tool. And this is making my Paperpile experience even better. Even if you stopped development on your PDF annotation today, I will still pay you for paperpile and continue using the annotation without more features. (Though, I will not pay you to use annotation :wink:)

One suggestion:
Publications in my field choose not to print page numbers. Other PDF viewers have some way of giving this information, either by showing the page number on the scroll bar (when you click and scroll), or in the top toolbar as “Page 1/10”.
It would be useful to have page numbering in some form, other than having to count the pages manually.


The page numbering is already implemented and will be part of the new beta expected end of next week.


Hi, really excellent annotation tool! After a few tries I only had a minor issue. I have some older PDFs with a messed up OCR text. When I highlight, the annotations show the errors in the underlying text (some words are just semi-random characters):

I know the problem lies in the original PDF. But do you think there is a way to overcome these errors? Maybe the text from the annotations could be editable? It is not a big deal since you can quickly click in the annotation and read the actual highlighted text. It might be an issue once the “Download annotations” is implemented.


Don’t know if it’s implemented in the current beta. But you can double click the text in the left hand panel and edit it. We thought about that. If it’s not in there it will be with the next beta.

Thanks for the feedback!