Pages. If you are aware of a PDF template for the sheet, that will give you the exact "breaks" for the stickers. Download it.
Put Pages in Page layout mode (File menu, Convert to Page Layout). Drop the downloaded PDF template on top of it, size it to full page (right to the edges- no margins).
Put content for your stickers onto the template in text boxes that fit within the sticker template borders. You can insert images too if you like. ANOTHER way to do this is to make a table with the same number of rows & columns of stickers and get the borders of the table cells aligned with the template sticker edges. Insert your text in the table cells.
PRINT a mockup to paper, then lay one of the blank adhesive sheets atop the printed one, hold it up to a bright light so you can visually see that you have proper alignment for all stickers. If so, you are ready to print to the adhesive paper directly. If not, tweak your text box or table rows/column positions accordingly, print again, hold it up to light to check alignment.
Once you have it aligned, print to the adhesive paper.
If there is NO template PDF, you need to measure the stickers edges on the adhesive paper. If me, in DTP mode in Pages, I'd turn on Rulers (View menu, Show Ruler) and then drag guide lines from rulers to line up with with the edges of each row (& column) of stickers. For example, if the middle edge of two side by side stickers was at- say- 4.25", I put a guideline at 4.25". If each row of sticker was- say- 1" tall, I put a horizontal guideline where the first sticker begins from the top of the page and then additional lines for each row of stickers 1 more inch down the page. Thus, if there was- say- 10 total stickers on a page in 5 rows, I've got the very top gridline, then one between row 1 & 2 & 3 & 4 and one more at the bottom of row 5. Between those horizontal lines and my middle vertical one, I've now got my "cell"s for content mapped out that should perfectly align with the adhesive cell zones.
That would basically mark off where sticker text (& optional images) can go. Then, same as above. Mockup a page, print to paper, hold up to light to be sure you have good alignments, etc.
