I have several PDF files/images that I want to merge to one file. Each page in the PDF is actually an image. Here is what works best for me.

Merge PDF files#

Use pdfunite from poppler-utils package:#

Pdfunite provided by package poppler-utils can be used to achieve our goal:

pdfunite a.pdf b.pdf output.pdf

The size of produced PDF file is small (about the sum of size of a.pdf and b.pdf). The image quality is well preserved.

Use convert from imagemagick:#

convert a.pdf b.pdf output.pdf

The images in the produced pdf have very poor quality and is blurred to be hardly recognizable. We can use -desnity option to increase the image quality:

convert -density 200 a.pdf b.pdf output.pdf

This time, the image quality improves greatly, but the size of produced file also increases greatly (significantly larger that what is produce by pdfunite).

Overall, using pdfunite is the best choice.

Merge images to produce a PDF file#

To merge several iamges and produce a PDF file. We can use convert from imagemagick:

convert img1.jpg img2.jpg output.pdf

We can also use img2pdf for this:

img2pdf img1.jpg img2.jpg -o output.pdf

Reference#

• Merge / convert multiple PDF files into one PDF
• How to merge pdf:s using Imagemagick (resolution problem): https://superuser.com/q/54041/736190
• Convert images to PDF: https://stackoverflow.com/a/8955457/6064933