PDF reader
Reading software is the program that opens a PDF and puts it on a screen.
In more detail
There is a long list of them and most people run two or three without thinking about it: Adobe Acrobat Reader (Windows, Mac, Android, iPhone), Preview (supplied with the Mac), Chrome, Firefox and Edge (each carries one of its own), Okular and Evince (Linux), SumatraPDF (Windows).
Two different things are easily called by one name, and this site keeps them apart. The reader is the person: they read the document, fill in its boxes, tick, sign, notice that a column does not line up. The reading software is the program: it shows the page, draws the lettering, lists the layers in a side panel, jumps to the page a link names.
Keeping them apart matters because they answer different questions. What a person can do with a document depends on how it was written; what appears on the screen depends on which program opened it, and the same file is entitled to look slightly different in two of them.
What it does on a real document
A PDF states wishes as well as ink. It may ask to open on the contents page rather than the cover, to stand the list of chapters open beside the page, to fill the window with the drawing rather than the paper around it. Each program decides for itself how much of that to honour: a program installed on the machine (Adobe Acrobat Reader, Preview, Okular) follows most of it, and the one built into a browser (Chrome, Firefox, Edge) follows very little.
The same holds for what a document asks not to be done to it. A file may ask that its text not be copied; Chrome greys the entry out, Firefox copies all the same. Neither is broken, and that is the whole point: the document asks, and each program answers for itself.
What no program is free to reinterpret is the drawing. The lettering carried inside the file, the colours stated against a profile and the position of every mark on the sheet come out the same everywhere, which is what makes a PDF worth sending in the first place.
Where it comes from, and why
English calls both the person and the program a reader, which is where the confusion starts; other languages have to choose. This site chooses: the reader is the person, and the program is named as software, everywhere and without exception.
See it on a finished document
A handbook that says how it wants to be read A document that reads freely and asks not to be copied
Glossary
- colour profile
- A file that says what a colour actually looks like. Without one, the same red is one red on your screen and another on a press. A document meant for print carries the profile its colours were chosen against.
- CMYK
- The four inks a printing press lays down: cyan, magenta, yellow and black. A screen mixes light instead, so a document going to a press states its colours in inks, not in screen colours.
- layer
- A named group of things drawn on a page that a reader can switch on and off, like tracing paper laid over a plan. A drawing can hold its measurements on one and its notes on another, and a layer can be set to show on screen and stay off the printer.