I am creating a book for publication with Blurb and all of my images have an exclamation point in the upper right hand corner. Each has a different message as to what the ppi is and what it will print at. All of my images are 300 dpi and 1000px at their largest side. What am I doing wrong? My understanding is for print, 300 dpi is the best HQ resolution. Will I need to resize all in Photoshop and start over and if so, what is the best size for such a project? Thank you.
Your problem is in the 1000px max, not the 300 ppi. 1000px photos are just good enough for small prints. There is no point in trying to print such small files, you need bigger than that, To find out the print dimensions just divide the number of pixels by the print resolution (the usual 300 ppi, but 240 ppi is usually enough for a quality print) . So you'll get a little more than 3.3 in if printed at 300 ppi, 4.1 in @ 240 ppi.