It is a common superstition among people working with computers that some certain softwares are obligatory. When you seek a job, you're commonly asked to own and be good at such softwares. Job posts for freelancers are even made with "blah blah is a must" in the title. But is that really the case? Many proprietary softwares are well-advertised, and usually backed by collaborating firms, and hence are displayed as if they are the best and even the sole choice.
But this usually is not the case. The most advertised is not always the best, and sometimes has a much better rival. And sometimes this rival might be free of charge.
Take most CAT softwares for instance. These tools are quite useful for translators with regard to saving time, particularly with regard to translations between European languages such as English, French and German. Some CAT softwares are much more preferred over others and even seen as obligatory by both translation agencies and clients. Files for translation are served in formats opened only by certain CAT tools. But this does not make those CAT tools undisputable. Indeed, sometimes these much-adored CAT tools even may be compromised against much overseen free tools like Google Translate. Though Google Translate is usually regarded as useless for professional use, it is quite helpful for translation between European languages. I usually read texts written in European languages such as French or Spanish with the after translation with Google Translate to English and it very rarely fails. Furthermore, Google Translate - though usually refused by most clients who even add some "No Google Translation Please" to their translation job posts - is sometimes superior to so-called professional CAT tools. I have once had to work with one of those world-famous CAT tools and found out that it did not do anything better and sometimes was much worse than Google Translate. Thus far I am using Google Translate to translate between European languages. And for translation between unrelated languages, nothing is a match for human brain. Different CAT tools indeed don't differ from one another. And if you still want something you should download and install on your computer, or something with a community you can use free and commonly used CAT tools such as Omegat that can be installed on a computer, or something available through your browser such as Matecat and Smartcat.
If you need some office suite, you can directly use Google's Google Docs service. However, Google Docs is still in state of development and maybe you would like to install Libre Office on your computer. This is a quite cool software, enabling you to write scripts, make graphics and presentations and work on spreadsheets. Though Google Docs is more compatible with commonly used .docx and .ppt format files, I must say the file formats used by Libre Office are much better and use of them should be encouraged. Besides, Libre Office is superior to Google Docs with regard to precision in generating PDF files; Google Docs still may generate erroneous PDF files. For page design, Scribus comes as a cool alternative.
If you're working with graphics, Inkscape can be your tool for generating vector graphics. It can look quite difficult in the beginning, but free tutorials both in text and video formats are available to learn its GUI. For those interested in photo editing, GIMP is available as an open-source alternative. For those who are accustomed to a well-known proprietary photo editor and regard the GUI of GIMP as difficult to learn, Gimpshop presents a familiar GUI. GIMP and Inkscape have recently been combined in a mobile application called GIMP Inkscape. If you want to make 3D graphics and animations, Blender3D is a choice beyond perfect. To prove that, the open movies have been made. Also, Sketchfab exists as a browser-based alternative.
So, if you've gathered your free open-source weapons, welcome to the battlefield. Fight!