This is a way to convert multiple pdf files in a folder into pngs.

Pngs are preferable because they cause less crashes when dragged into presentation software, retain see-through background, and can be smaller in size if the pdf has too many overlapping graphics.

Go to your home folder

cd ~

Check for hidden files. You are looking for a .bashrc or .profile file.

ls -a

Open with a text editor, e.g.

nano .profile

Add the following

function pdf2png {
mkdir $1
sips -s format png *.pdf --out $1
}

save and close the file.

Now open a new terminal window. This reloads the commands in the profile file

try

sips

If it thinks it is a command you are good to go.

Go to a folder with pdf files

cd pdf_folder/

pdf2png outpng

This makes a new folder named 'outpng' with all pdfs converted to png.

Sips stands for Scriptable Image Processing System and can convert from the following formats: jpeg, tiff, png, gif, jp2, pict, bmp, qtif, psd, sgi, tga

For more sips options look into

sips --help