1. Measure the useful area, not the whole page
A label can occupy only a small part of an A4 PDF. Shrinking the entire page also shrinks its surrounding white space and makes the label unnecessarily small. Cropping selects the useful region; resizing fits that region into a slot.
A4 is 210 × 297 mm. A geometric division into four gives 105 × 148.5 mm cells. These are theoretical dimensions: margins and spacing may make the actual usable area smaller. This division is not a promise that every carrier accepts those label dimensions.
2. Calculate one scale factor
For a region of width W and height H placed inside w × h, the largest non-overflowing scale is the smaller of w/W and h/H. Multiply both dimensions by that factor. A 90-degree rotation exchanges W and H.
Purely geometric example: a 100 × 150 mm region inside a usable 95 × 140 mm area gives ratios of 0.95 and 0.9333. The limiting factor is about 93.33%, giving a 93.33 × 140 mm output. These values explain the calculation; they do not specify your printer margins or a minimum barcode size.
3. Understand double scaling
A first scale of 90% followed by printing at 95% gives 0.90 × 0.95 = 0.855: the content is 85.5% of its original dimensions. Percentages multiply; they are not added.
The final PDF is already composed, so begin printer checks at actual size. The calibration page has a 100 mm line to measure after printing. A 95 mm measurement reveals a 95% effective scale without changing any real labels just to test the driver.
4. Stop shrinking when information is no longer readable
Preserve complete codes, their clear surrounding space, text tracking references and useful small print. Do not stretch only the width to fill a slot. Shrinking a blurred photograph does not recreate detail missing from the source.
Compare the original, preview and a physical test print. When information becomes too small or a carrier specifies incompatible dimensions, retain the source format or choose a suitable printing method. Four labels per sheet is a layout option, not a requirement for every document.
| Operation | Effect | Check |
|---|---|---|
| Crop | Exclude a document area | No useful information disappears |
| Resize proportionally | Reduce width and height together | Codes are not stretched |
| Fit when printing | Potentially apply a second scale | Measure the calibration line |
Practice, then check
Teaching PDFs are fictitious, contain no customer data and are not valid postage. They do not replace a physical print or carrier check.
Calibration PDF: a 100 mm reference lineA dimension calculation does not prove scanner readability. Carrier instructions remain authoritative.
Sources and method
Workflow instructions describe Label2A4; numerical examples are calculations, not carrier acceptance tests.
Adobe Acrobat: PDF page size and printingLabel2A4 method and limitations