If you're willing to use a terminal, you can use ImageMagick. Install it with

sudo apt install imagemagick

then you can do:

convert image1.jpg image2.png text.txt PDFfile.pdf outputFileName.pdf

It worked for me, but the problem is it converts the text.txt file into an image, so you can't highlight the text in the resulting pdf.

Install pdftk

sudo apt-get install pdftk

Pdftk

If PDF is electronic paper, then pdftk is an electronic staple-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses. Pdftk is a simple tool for doing everyday things with PDF documents.

You can create pdf files from text or images with Libre Office then to stitch these togeter with other pdf files

pdftk 1.pdf 2.pdf 3.pdf cat output 123.pdf

It can also

• Split PDF Pages into a New Document

• Rotate PDF Pages or Documents

and a lot more besides

More details here: Ubuntu Geek: List of PDF Editing tools

Try PDF Chain:

PDF Chain is a graphical user interface for the PDF Toolkit (PDFtk). The GUI supports all common features of the command line tool in a comfortable way.

You can install it either from the default repos, or get the latest and greatest from PDF Chain PPA.

sudo apt-get install pdfchain

Or PDF Mod:

PDF Mod is a simple application for modifying PDF documents.

You can reorder, rotate, and remove pages, export images from a document, edit the title, subject, author, and keywords, and combine documents via drag and drop.

sudo apt-get install pdfmod

See also:

• How to copy from a pdf to another pdf in ubuntu/linux

For multiple files inside a directory and its subdirectories with different extensions I couldn't find a neat answer, so here it is

convert -quality 85 `find -type f -name '*.png' -or -name '*.jpg' | sort -V` output.pdf

I used command substitution to pass the selected items returned by find command as an argument to convert command. Unfortunately sort -n didn't sort my files correctly so I tried -V option and it did the trick. Also make sure the name of your files and directories are in natural sort order in advance. For example dir1, dir2, dir3 not dir1, dir_2, dir3.

Install Master PDF editor. The tool offers creating, merging and extracting PDF files. Check here for details about master PDF editor and installing it on Ubuntu

This is the solution i used to convert multiple TIFFs to PDFs.

I had to create more than 6.000 PDFs starting from 30.000 tiffs. convert estimate time: 6 to 7 hours.
I used tiffcp and tiff2pdf, they took few seconds.

$ tiffcp 1.tiff 2.tiff ... multi.tiff
$ tiff2pdf multi.tiff > final.pdf

This way is really fast because images are not converted, just packed.

Maybe there are some tiff formats that doesn't work so easily, for me it worked perfectly.

Hope it helps.

I can't believe nobody has mentioned latex (tex) yet. It is specifically designed for producing documents, and can combine text, images, and PDFs into a 'master' document (without any degradation of quality). It is a full suite of libraries and an extensible markup language, basically - it's been around since forever and highly used in the scientific community, still.

Technically, it's a typesetting language.

Adding on the community answer above, you can do convert 'ls *.jpg -tr'. To force the PDF file to have the images in chronological order.

Try LaTeX with pdflatex.

I had never used it before but it took me about 10 minutes to start making .PDFs with it and about 40 minutes to get them customized exactly as I wanted. I included the best formatting guides I found, at the end.

sudo apt-get install pdflatex && sudo apt-get install texlive

Basically you create one .tex file - for example hello.tex - with the LaTeX language, then run pdflatex hello.tex on that file and it will generate the PDF. The basics of the language can be found here: http://www.maths.tcd.ie/~dwilkins/LaTeXPrimer/

Here is a barebones example .tex file:

 \documentclass[a4paper,10pt]{article}

 \begin{document}

 {\footnotesize
 YOUR TEXT HERE

 YOUR TEXT HERE
 }

 \end{document}

Optional extra formatting:

To add images: https://www.sharelatex.com/learn/Inserting_Images

For different font sizes: https://www.sharelatex.com/learn/Font_sizes,_families,_and_styles

For different fonts: https://www.sharelatex.com/learn/Font_typefaces

To change page size and margins when using pdflatex: \usepackage[pass,paperwidth=148mm,paperheight=210mm,margin=5mm]{geometry}

For multi-page pdf:
Convert all files to pdf, then join using a pdf writer eg. pdftk, pdfill, Microsoft Print to PDF, CutePDF, etc

For single-page pdf:
Convert all files to images eg. PNG, named in sequence. Then join to one page with image converter eg. imgconv

imgconv.exe -append *.png out2.pdf (for vertical)
imgconv.exe +append *.png out2.pdf (for sideways)

There might be some converters that can manipulate in other formats or even process with native input formats before outputting to pdf. All programs mentioned here are free.