Linguistic Annotation and Visualization Tool for PDF Documents
Latest commit c8c459b Aug 11, 2018


PDFAnno is a browser-based linguistic annotation tool for PDF documents.
It offers functions for annotating PDF with labels and relations.
For natural language processing and machine learning, it is suitable for development of gold-standard data with named entity spans, dependency relations, and coreference chains.

If you use PDFAnno, please cite the following paper:

Hiroyuki Shindo, Yohei Munesada and Yuji Matsumoto,
"PDFAnno: a Web-based Linguistic Annotation Tool for PDF Documents",
In Proceedings of LREC, 2018.

It is highly recommended to use the latest version of Chrome. (Firefox will also be supported in future.)


If you install PDFAnno locally,

git clone
cd pdfanno
npm install
cp .env.example .env

Then, edit .env as you like.
The default values are:


Run Server

npm run server


  1. Visit the online demo with the latest version of Chrome.
  2. Load your PDF and annotation file (if any). Sample PDFs and annotations are downloadable from here.
  3. Annotate the PDF as you like.
  4. Save your annotations via button.
    If you continue the annotation, respecify your directory via Browse button to reload the PDF and anno file.

For security reasons, PDFAnno does NOT automatically save your annotations.
Don't forget to download your current annotations!

Annotation Tools

Icon Description
Span highlighting. It is disallowed to cross page boundaries.
One-way relation. This is used for annotating dependency relation between spans.
Rectangle. It is disallowed to cross page boundaries.

Annotation File (.anno)

In PDFAnno, an annotation file (.anno) follows TOML format.
Here is an example of anno file:

pdfanno = "0.4.1"
pdfextract = "0.2.4"

id = "1"
page = 1
label = "label1"
text = "AgBi 0.05 Sb 0.95 Te 2"
textrange = [1422,1438]

id = "2"
page = 1
label = "label1"
text = "0.48 Wm [NO_UNICODE] 1 K [NO_UNICODE] 1 )"
textrange = [1386,1397]

head = "1"
tail = "2"
label = "relation1"

where textrange corresponds to the start and end token id of pdftxt.
pdftxt is a text file extracted from the original pdf file.
You can download pdftxt via pdf.txt button at the top right of the screen.

Reference Anno File

To support multi-user annotation, PDFAnno allows to load reference anno file.
For example, if you create a.anno and an another annotator creates b.anno for the same PDF, load a.anno as usual, and load b.anno as a reference file. Then PDFAnno renders a.anno and b.anno with different colors each other. Rendering more than one reference file is also supported.
This is useful to check inter-annotator agreement and resolving annotation conflicts.
Note that the reference files are rendered as read-only.


Please contact hshindo or feel free to create an issue.