I had the task this week of resizing two Adobe Acrobat PDF files for a website, so they would be around 950 pixels wide - a task that was a bit of a puzzler as Acrobat doesn't allow you to change/scale the size of your pages and resave the file. In the case of these two PDFs I didn't have access to the original files, which were created in InDesign.
I tried a few things. I tried to trick my full version of Acrobat into printing to a PDF with the size scaled, but Acrobat was smarter than me and told me to 'save as' instead. Naturally the size didn't scale.
I tried opening the files as individual JPGs through Photoshop and resizing. The original files opened up as around 1300 pixels wide, which is a bit too wide for viewing through a web browser on many computers unless you have a largish widescreen monitor. Of course, browsers like Firefox will simply open the PDF using Acrobat itself externally from the browser, so zooming isn't a problem, but Safari likes to cleverly open PDFs through its own browser window, and the initial view of 1300 pixels wide was ungainly to navigate. Photoshop didn't produce the results I wanted, so I tried using other suggested programs to work on the files. Illustrator was a non-starter, trying to replace fonts I didn't have with fonts I did, which would have changed the look of the file from the original.
Finally I tried opening the PDF through Preview, which is a standard program on Apple Macs. At last I had a solution! Preview allowed me to scale the image AND save as a PDF from its Print menu. By scaling the pages to about 70% of the original, I could produce a file under 900 pixels wide, a great match for my website.
If only Adobe would add a page size/scale feature to Acrobat, I could have saved more than an hour of messing around and google searching for solutions that didn't work.
If you're looking for a way to resize/scale PDF pages for a website, try Preview. You'll keep the quality but not the real estate.