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There was a time people printed papers for reviewing. Double-spaced text with tables and figures at the end. Well, with devices like the iPad, people need not print papers anymore. If paper is better for you, that’s ok, I understand, but there’s no longer a “need to print”. Today you have apps where you can read PDF files, make annotations and export them. The question is: what app is best to review a scientific paper?

I’ve been using several over the years and confess none of them fully satisfies me. My perfect app for reviewing should 

– be able to pop-up figures with a click when they’re mentioned

– make notes linked with a certain line or range of lines in the text

– ability to make free comments, as most already do

– write equations using LaTeX

– use markdown language as well

– and finally, and most important, be able to export these comments in a simple and easy to read fashion, allowing me to copy and paste into the boxed reserved for this at the journal’s website.

My purpose in this post is not to make an extensive review of the apps I used, but share my experience and why I changed.


In the early days of the iPad, I reviewed papers with iAnnotate. One of the main advantages was selecting a part of the PDF, like an image, and copy/paste it next to the part of the text mentioning the figure. Thus, when I read the authors analysis, I could easily access the figure to see the results. I could add notes, and write in the margins, as in most PDF annotation apps. An interesting feature is the ability to go directly to a page farther away, see a figure for example, and go back to the page where I was reading, like we do with webpages with hyperlinks. But…

If I wanted to export my notes, I couldn’t. This means I needed to split my screen into the annotated PDF and a Notes app where I compiled my comments. Also, the handwriting trace became sluggish with a few updates and I looked for alternatives.


This is when I tried PDF-notes. It was faster than iAnnotate, the handwriting trace is better, and I could easily write something in the text by double-tapping the screen to zoom the area where I wanted to annotate something. However, I lost the ability to have figures accessible. Even so I tried to compensate with a small page scroll at the bottom for an easier access to the images.

I used this app for a long time, but the method for compiling my notes was still the same and some features I had on iAnnotate were no more. However, the experience compensated these lacks because I didn’t return to iAnnotate. But then something happened.

PDF Expert

For some reason I became tired of PDF notes. Maybe some operations demanded too many steps, and I looked for a different experience. This is when I found Readdle’s PDF Expert. One of the major advantages was the sync between the iPad and the mac apps. This made compiling the notes much easier. In fact, a good synching was the major problem I experienced with PDF-notes.

The app had all the features for quality handwriting, comments insertion, it is fast and the page grid view makes accessing any page easier without intermediate steps uploaded the annotated file to a cloud like Dropbox. I still miss the image capture feature of iAnnotate, the double-tap to zoom of PDF-notes, but the synching and user experience compensates that. Until I found another surprising app.


This app is out-of-the-box. It’s still not my perfect paper reviewing app, but closer. Finally, I got the figure capture feature back. I’m able to make annotations relatively to a part of the text, or free comments. There’s this neat feature of pinching to shrink the PDF (hard to explain, you need to see it!) allowing me the access to a figure while I read the authors analysis. Free handwriting on a side area independent of the document. But these are not the most important feature.


Finally I can export or copy to the clipboard my comments, including the page in the document. This is a major change in the hard-compilation scheme I had and the main reason I changed. Synching to cloud services could be better, but not a problem because of the export feature.

 I focused on apps for the iPad because that is my ecosystem, but I’m sure there are similar apps in other platforms. If you have an experience with reviewing papers with apps in Android or Windows, share your experience in the comments for others.

QUESTION: Do you have a great paper reviewing experience with one of these, or any other app you’d like to share?