Adobe Reader

Adobe Acrobat Reader is the default PDF viewer that most people end up with because it comes pre-installed or gets suggested every time you open a PDF somewhere. It is free, made by Adobe, and available on Windows, macOS, iOS, and Android. The free version handles viewing, printing, form filling, commenting, and digital signatures. Anything beyond that - editing text, converting to Word, merging files - requires Acrobat Pro, which is a paid subscription.

The elephant in the room is the size. The installer is around 700 MB and takes about 2 GB on disk once installed. For a program that most people use to read and print PDFs, that is a lot. SumatraPDF does the same basic job in 3 MB.

What it does

Open any PDF and you get a tabbed interface with zoom, page navigation, full-screen reading mode, and text search (Ctrl+F). The commenting tools let you add sticky notes, highlight text, underline, strikethrough, and draw freehand. Fill & Sign (Tools > Fill & Sign) recognizes form fields and lets you type into them, then place a signature you draw with your mouse or type out.

The free version stops there. If you need to edit the actual text in a PDF, convert it to Word or Excel, run OCR on a scanned document, merge multiple PDFs, or password-protect a file, you need Acrobat Pro or one of the free alternatives that handle some of these tasks.

Who it is for

If you just read and print PDFs, your browser or SumatraPDF will do the job faster and lighter. Acrobat Reader makes sense if you regularly fill out forms, need the annotation tools, or receive PDFs that do not render correctly in simpler viewers.