The annotation layer works well for displaying the form elements in the browser, but it was not compatible with the way PDF.js supports printing. We render this annotation layer, composed of HTML elements, on top of the canvas layer. Then, we send them out from the worker and render them in the main process using HTML elements inserted in a div (annotation layer). In PDF.js, we parse a PDF file and create the annotations in a web worker. AcroForm annotation elements support user input similar to HTML input e.g. They are often used for things like taking notes on a document or drawing on top of a document. Annotations in PDF are separate elements from the main content of a document. Within a PDF file, the form elements are stored in the annotation data. Filling Forms (AcroForms)ĪcroForms are one of two types of forms that PDF supports, the most common type of form. They support form filling and we will describe them in more detail below. The other two layers are the Annotation/AcroForm layer and the XFA form layer. It contains span elements that are transparent and line up with the text drawn below them on the canvas.

The first layer, the text layer, enables text selection and search. PDF.js sends them to the main thread and draws them on an HTML5 canvas element.īesides the canvas, PDF.js potentially creates three more layers that are displayed on top of it. The parsed document will then generate drawing instructions. To understand how we added support for forms and tagged PDFs, it’s first important to understand some basics about how the PDF viewer (PDF.js) works in Firefox.įirst, PDF.js will fetch and parse the document in a web worker.

Below we’ll describe how we implemented the form support, improved accessibility, and made sure we had no regressions along the way. While we invested more time in the PDF viewer, we also went through the backlog of work and prioritized improving the accessibility of our PDF reader for users of assistive technologies. We decided it was time to reinvest in the PDF viewer (PDF.js) and support filling PDF forms within Firefox to make our users’ lives easier. Firefox supported displaying PDF forms, but it didn’t support filling them: users had to print them, fill them by hand, and scan them back to digital form. Last year, during lockdown, many discovered the importance of PDF forms when having to deal remotely with administrations and large organizations like banks.

Fire fox pdf reader