When you configure PDF Stamping for your ebook, once the buyer completes checkout and proceeds to their thank-you page where we present their download links, there may be up to several seconds' delay while our system waits to receive the buyer's info from the payment processor, so we can stamp that info into the copy of your PDF ebook that they will download.
Even after we receive the buyer's data from the payment processor, extremely large/complex PDFs can take longer to stamp than a buyer may be willing to wait, so in that case our thank-you page will eventually give up "stalling for time" before things get too frustrating for the buyer, and it will let them download their file whether the stamping process had finished by then or not. Later downloads on the same link would have the stamp, since by that time the Stamper would have finished stamping the file.
Optimize Your PDF
Our PDF Stamper can have trouble stamping files larger than about 100 MB or so by the time the buyer reaches their download page. See if you have options to "optimize" your PDF for a reduced filesize when you save or export it from the app where you created it. Adobe apps like Acrobat and InDesign usually label this option as "Optimize for Fast Web View" or similar.
Especially consider having your PDF authoring app resample images to match the size they'll be displayed at -- e.g., even a large HD monitor can only display about 2 megapixels across the entire screen, so there's no advantage in retaining a high-resolution photo at its original multi-megapixel size when it will only be shrunken to fit within the layout of a PDF page viewed on a lower-res monitor anyway, where all those extra image pixels simply go to waste. The buyer's computer/device may also struggle to load each high-res image and resize it on-the-fly, resulting in laggy PDF viewing and subpar image quality as-viewed, whereas your PDF authoring app will probably do a better-quality job of resizing images preemptively.
Delay the Buyer's First Download Attempt
If you're not able to get the file size under 100 MB, you can still avoid offering the buyer an unstamped file and avoid stalling them after checkout by setting up a Common Thank-you Page URL. Buyers proceeding from checkout would immediately be redirected to that thank-you page on your own site, rather than the E-junkie-generated thank-you page where they could download your ebook right away. We'd suggest having your page advise buyers to watch their email for further instructions, and to check their Spam folder in case the message winds up in there and mark it as Not Spam if so.
To download their ebook, they would need to wait for the thank-you email we send for each product, which provides a link to reach the E-junkie-generated thank-you page with their actual download link, and by that time the Stamping process should certainly have finished. Make sure you have not disabled the Product Thank-you Email in the settings of each download product. If you have a Common Thank-you Email (all new accounts are given one by default in Seller Admin > Manage Seller Account > Edit Preferences), please see also this page for important tips.