While there is no single official "Journal 1" PDF in Spanish on the Internet Archive
Fan-Created Content: There is no official version of Journal 1 that contains the complete story written by Alex Hirsch. Most "Diario 1" PDFs on the Internet Archive are fan projects that piece together frames from the show with original art to fill the gaps. gravity falls diario 1 pdf espa%C3%B1ol internet archive
Internet Archive: You can find fan-compiled versions, the official "Journal 3" in various languages, and newer releases like "The Book of Bill" (El Libro de Bill). While there is no single official "Journal 1"
If you are looking for physical copies of official books in Spanish, they are often available through major retailers: Gravity Falls: Diario 3 : Available at Amazon.es and MercadoLibre El Libro de Bill (The Book of Bill) “Diario 3” (tapa dura) – Edición en español
: Multiple users have uploaded Spanish PDFs of fan-made Journal 1 reconstructions. You can view these at Scribd - Gravity Falls Diario 1 Scribd - Diario 1 PDF Official Content