How to create large PDF files (10MB, 50MB, 100MB, 200MB, 500MB, 1GB, etc.) for testing purposes?

The most simple tool: use pdftk (or pdftk.exe, if you are on Windows):

pdftk 10_MB.pdf 100_MB.pdf cat output 110_MB.pdf

This will be a valid PDF. Download pdftk here.

Update: if you want really large (and valid!), non-optimized PDFs, use this command:

pdftk 100MB.pdf 100MB.pdf 100MB.pdf 100MB.pdf 100MB.pdf cat output 500_MB.pdf

or even (if you are on Linux, Unix or Mac OS X):

pdftk $(for i in $(seq 1 100); do echo -n "100MB.pdf "; done) cat output 10_GB.pdf

Windows: fsutil

Usage:

fsutil file createnew [filename].[extension] [# of bytes]

Source: https://www.windows-commandline.com/how-to-create-large-dummy-file/

Linux: fallocate

Usage:

fallocate -l 10G [filename].[extension]

Source: Quickly create a large file on a Linux system?

For those using macOS mkfile might be a good alternative to fallocate or dd

mkfile 100m some100mfile.pdf

reference - https://stackoverflow.com/a/33478049/711401

I had problems using pdftk with the cat parameter had a better success with output.

The following command worked for me:

pdftk file_1.pdf file_1.pdf file_1.pdf file_1.pdf cat output.pdf

Using cat produced the following error:

Error: Unexpected text in page range end, here: 
    output.pdf
    Exiting.
    Acceptable keywords, for example: "even" or "odd".
    To rotate pages, use: "north" "south" "east"
        "west" "left" "right" or "down"
Errors encountered.  No output created.
Done.  Input errors, so no output created.

http://www.pdflabs.com/docs/pdftk-cli-examples/.

I created a 172mb PDF is no time at all.

according to http://www.maketecheasier.com/combine-multiple-pdf-files-with-pdftk/ the command should be

pdftk file1.pdf file2.pdf file3.pdf cat output newfile.pdf

note that you should download windows version of pdftk