Photoshop and Illustrator are two of Adobe's most popular graphics programs. ... Photoshop is a popular choice for web graphics, photo editing and ... and then send them over to InDesign if you're working on a book or PDF
i have a pdf file of size 266KB which I open with Photoshop, crop out the boundaries and save it back again. The new file size is 7.96MB!
Modify the PDF in Illustrator or Acrobat, not Photoshop, if you want to retain the vector information and small file size.