update README

README.md

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-# pdftag
-Edit PDF metadata
+# Pdftag
+A simple metadata editor for PDFs
+
+![pdftag](pdftag.png)
+
+## Introduction
+
+The main goal of Pdftag is to provide a simple and usable solution to edit metadata found in PDFs.
+
+Other more complex solutions exist to manipulate PDFs, but they may have dependencies on Java and may be not completely free.
+
+This project makes use of the [poppler] library for all the PDF information reading and writing.
+
+It is written in [Vala] and [GTK+], meaning it is fast and has a small memory footprint.
+
+## Features
+
+Pdftag supports editing the following PDF tags:
+
+- Title
+- Author
+- Subject
+- Keywords
+- Producer
+- Creator
+- Creation date
+- Modification date
+
+It also displays useful non-editable information:
+
+- PDF format
+- Number of pages
+
+## Compiling and installing
+
+To build Pdftag you need the following dependencies (including development files):
+
+- meson (build only)
+- ninja (build only)
+- vala (build only)
+- gtk3
+- poppler-glib
+
+Then run
+
+```
+meson --prefix=/usr/local (or your preferred installation prefix)
+ninja -C build
+ninja -C build install
+```
+
+[poppler]:https://poppler.freedesktop.org/
+[Vala]:https://wiki.gnome.org/Projects/Vala/
+[GTK+]:https://www.gtk.org/