https://www.judiciary.senate.gov/imo/media/doc/Kavanaugh Summer 1982 Calendar Pages1.pdf
Notice how the "Dr Strawberry" text in the center is all pixillated, but other text is not? Also the "Co" in "Columbia". The reason is that the documents was editing in Adobe Acrobat with automatic OCR turned on (this is the default setting).
This means Adobe tries to recognize text in the image, and it will create a custom high resolution vector font for each bit of text. You can see this if you try to edit it in Acrobat:
Depending on how good the handwriting is, it will either convert it, or not convert it. If it can't figure out what it is, then it will not convert it.
This exact same problem happened with Obama's birth certificate.