Occationally you may find some PDFs that do not start on page one, or that show up at a different zoom than you expected. When this happens you may find that moving to page one, resetting your zoom, then saving the file doesn’t actually fix the problem.
If this is an issue you’ve run into, there is a fix for Acrobat Pro owners.
1) Open your PDF and choose Document > Extract Pages to extract all the pages one by one
2) Select File > Create PDF > Merge Files into a Single PDF.
3) Drag and drop your individual files and then use File Size LARGER > Combine Files > Save
via macosxhints
There is also another, more cumbersome way to do this for those that don’t have Acrobat Pro.
1) Open your PDF file in Previews
2) Select every page of your document except the first page then select Edit > Delete
3) Save the one remaining page as an individual PDF
4) Repeat for every page of your document
5) Open the first page PDF file in Preview, then drag all other pages into your sidebar
6) Save As.
That’s not ideal for long documents, but if you’re looking at something short, and you don’t have Acrobat Pro this method can work.