How can reduce or change the Google photos and images size for pdf files.

Sir/Madam,
With respectfully I like to asking, how can reduce the Google photos or images size for converting to the pdf files. I have many times trying to convert small size photos as 1 Gb. or 50 kb but in our photo platform is not supporting or nor any key or options for changing the image sizes.
So, I request you kindly give suggestions for changing the photos size, because this days all the government and some private portal is not recommended the documents or files which is not matching with the requirements sizes of the file's. I hope you will give suggestions those tasks can easily solve.